Automated telescope alignment and orientation method

ABSTRACT

A fully automated telescope system is able to be fully operable in both Alt-Az and polar configurations. In either configuration, the telescope aligns itself to the celestial coordinate system following a simplified initialization procedure during which the telescope tube is first pointed north and then pointed towards a user&#39;s horizon. A command processor, under application software program control orients the telescope system with respect to the celestial coordinate system given the initial directional inputs. The initial telescope orientation may be further refined by initially inputting a geographical location indicia, or by shooting one or two additional celestial objects. Once the telescope&#39;s orientation with respect to the celestial coordinate system is established, the telescope system will automatically move to and track any desired celestial object without further alignment invention by a user.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 09/428,865, filed 26 Oct. 1999 now abandoned, entitled FULLYAUTOMATED TELESCOPE SYSTEM WITH DISTRIBUTED INTELLIGENCE, commonly ownedby the assignee of the present invention, the entire disclosure of whichis expressly incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to telescopes or other observationinstruments and, more particularly, it relates to fully automatedtelescope systems with distributed intelligence and control systems forsuch telescopes.

SUMMARY OF THE INVENTION

The present invention relates to fully automatic telescope systems whichare capable of performing alignment and orientation operations underprogram control with a minimum of intervention by a user. The telescopesystem is able to perform its alignment and orientation functionsregardless of whether it might be configured as an alt-azimuth telescopeor as an equitorial telescope. In accordance with the invention, thesystem is provided with sufficient processing power and with amultiplicity of application routines so that alignment and orientationis performed with regard to a large number of different algorithms andwith respect to a variety of user definable data type inputs. All thatis required is that some location index be provided to the system andthat the system's motors are initialized to a horizontal and verticalreferant. Time might be included as an input parameter, whether userprovided, or by automatic extraction from a peripherally coupled device.Location indices as well as horizontal and vertical referants might beuser provided, obtained under user direction, or automatically obtainedfrom various other peripherally coupled devices.

The telescope system has a distributed intelligence in that its motorcontrol functions are independently developed by motor modules includinga microcontroller, operating on motor movement commands received from ahand held command module, in combination with position feedbackinformation derived from optical encoders coupled to each motor shaft.Alternatively, the encoders might be coupled to each of a telescope'stwo generally orthogonal axes, and encoder feedback signals directed tothe motor module microcontrollers.

Distributed intelligence is further characterized in that the telescopesystem hand held command module might be provided in two separateconfigurations. A first configuration is simplified, and only providesdirection and speed commands to the intelligent motor modules. Systemintelligence thus resides in the motor modules with the command modulefunctioning more as a steering wheel, or directional joy stick.

In a second configuration, the command module is a fully functionalmicroprocessor controlled command unit, capable of executing high levelapplication software routines and performing numerous data processingtasks, such as numerical calculations, coordinate systemtransformations, database manipulations, and managing the functionalperformance of various different peripherally coupled devices.

A central interface panel is provided on the telescope system andsupports interconnection between and among the intelligent motormodules, the command module (of either form) and peripheral devices.Communication between and among the component parts is made over serialdata and control communication channels in accordance with a packetbased serial communication protocol. An RS-232 port is also providedsuch that a command module is able to communicate with ancillary RS-232capable devices like personal computer systems and/or a command modulebelonging to another intelligent telescope system according to theinvention.

Use of the various communication channels allows the telescope systemaccording to the invention to communicate with other devices in order toexchange stored information, exchange created and stored operatingroutines, obtain updates to programs and/or internal databases and thelike. In this regard, the telescope system includes a number of internaldatabases, including at least one database of the celestial coordinates(RA and DEC) of known celestial objects that might be of interest to anobserver. Further, the system includes a database of the geographicalcoordinates (Latitude and Longitude) of a large body of geographicallandmarks. These landmarks might include the known coordinates of citiesand towns, cartographic features such as mountains, and might includethe coordinates of any definable point on the earth's surface whoseposition is stable and geographically determinable. Each of thedatabases are user accessible such that additional entries, ofparticular interest to a user, might be included.

The solution to any given problem in celestial trigonometry depends onbeing able to convert measurements of obtained in one coordinate system(alt-az, for example) into a second coordinate system (the celestialcoordinate system). The present invention relates to a system and methodfor orienting a computerized telescope system of the type including atelescope coupled for rotation about two orthogonal axes, with respectto a spherical coordinate system. The telescope is provided with a pairof motors, each motor coupled to rotate the telescope about a respectiveone of the orthogonal axes. Each motor further includes a positionalreference indicator which defines an arcuate position of the telescopewith respect to its corresponding axis. Positional reference informationis taken from each positional reference indicator and provided to acontrol processor which is programmed to carry out the calculationsnecessary for effecting coordinate system transformation.

In a first line of procedure, the computerized telescope system is ableto locate its own alignment stars based on date and time entriesprovided by, a user during an initialization procedure. Specifically,the telescope is moved about one of its orthogonal axes until thetelescope is pointed at a first positional reference. In one aspect ofthe invention, the first positional reference is North.

After the telescope system is pointed to the first positional reference,the arcuate position of that positional reference indicator is recordedand stored by the control processor so as to define a first referenceposition. Next, the telescope is moved about a second axis in order toposition the telescope at a second reference point. In a particularaspect of the invention, the second reference point is the horizon, thuscausing the telescope to be leveled. The arcuate position of therespective positional reference indicator is read and recorded tothereby define a second reference point.

Particularly, the positional reference indicators are position encodersof altitude and azimuth motor assemblies. Pointing the telescope Northand leveling the telescope, functions to zero-in the position encodersof the altitude and azimuth motor assemblies. Any subsequent motion ofthe telescope away from its 0,0 position allows the telescope system todirectly calculate its altitude and azimuth displacements from the 0,0reference point.

Using time and date entries provided by a user, the telescope systemconsults a database of well known celestial objects and selects aparticular bright object which is currently above the horizon. Theentered time and date information allows the system to calculate whetherthat particular bright object has rotated sufficiently in rightascension to bring it above the observer's horizon, while a virtuallatitude and longitude entry provided by an observer's entering ageographical indicia, provides the system with sufficient informationregarding an observer's latitude such that it may calculate adeclination value for the desired viewing object.

The system automatically slews the telescope to the vicinity of thedesired viewing object by commanding the appropriate motion from thealtitude and azimuth motors. Once the telescope has slewed to thevicinity of the desired star, the observer is prompted to center thestar in the field of view of the telescope eyepiece. Once the star iscentered in the field of view of the eyepiece, the system calculates theposition and orientation of the telescope with respect to the night sky(the celestial sphere).

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentinvention will be more fully understood when considered with respect tothe following detailed description, appended claims and accompanyingdrawings wherein:

FIG. 1 is a semi-schematic perspective view of one embodiment of atelescope system in accordance with the present invention, configured inan initial, un-automated manner;

FIG. 2 is a semi-schematic perspective view of the telescope system ofFIG. 1, including semi-intelligent drive motors coupled to the telescopeaxes and illustrating alternative control systems.

FIG. 3 a is a semi-schematic partial perspective view of an electricalinterface panel in accordance with the present invention;

FIG. 3 b is a semi-schematic block diagram of the signal and busconfiguration of the electrical interface panel of FIG. 3 a;

FIG. 4 a is a semi-schematic exploded perspective view of asemi-intelligent motor assembly in accordance with the presentinvention;

FIG. 4 b is a semi-schematic block diagram of the electrical componentsof a semi-intelligent motor assembly in accordance with the presentinvention;

FIG. 5 a is a semi-schematic front view of an embodiment of asemi-intelligent dual-axis drive motor motion control system accordingto practice of principles of the present invention;

FIG. 5 b is a semi-schematic block diagram of the electronic componentsof the embodiment of the semi-intelligent dual-axis drive motor motioncontrol system of FIG. 5 a;

FIG. 6 a is a semi-schematic front view of an intelligent dual-axisdrive motor motion control system according to practice of principles ofthe present invention;

FIG. 6 b is a semi-schematic block diagram of the electronic componentsof the embodiment of the intelligent dual-axis drive motor motioncontrol system of FIG. 6 a;

FIG. 7 a is a simplified waveform diagram of ideal photodetector outputcharacteristics, illustrating a quadrature output pattern;

FIG. 7 b is a simplified waveform diagram illustrating photodetector“on” and “off” periods in accord with the invention;

FIG. 7 c is a simplified waveform diagram depicting dynamically tunedphotodetector output characteristics, exhibiting an ideal quadratureoutput pattern;

FIG. 8 is a conceptual flow diagram of an initialization procedure inaccordance with the invention;

FIG. 9 is a database table illustrating an exemplary location entry;

FIG. 10 a is a conceptual flow diagram of a first, “easy” alt-azalignment and orientation procedure in accord with the invention;

FIG. 10 b is a conceptual flow diagram of a second, single star, alt-azalignment and orientation procedure in accord with the invention;

FIG. 10 c is a conceptual flow diagram of a third, two-star, alt-azalignment and orientation procedure in accord with the invention;

FIG. 11 a is a conceptual flow diagram of a first, “easy” polaralignment and orientation procedure in accord with the invention;

FIG. 11 b is a conceptual flow diagram of a second, single star, polaralignment and orientation procedure in accord with the invention;

FIG. 11 c is a conceptual flow diagram of a third, two-star, polaralignment and orientation procedure in accord with the invention;

FIG. 12 is an exemplary line listing of a communication packet inaccordance with the interface protocol of the invention;

FIG. 13 is a simplified partial perspective view of a uniformillumination lightbox;

FIG. 14 is a perspective view of a second embodiment of a telescopeaccording to the invention, having integrated motor assemblies;

FIG. 15 is a simplified, exploded, partial perspective view of adeclination (altitude) motor assembly integrated into a fork arm of thetelescope of FIG. 14;

FIG. 16 is a simplified, partial perspective view of a right ascension(azimuth) motor assembly integrated into the base housing of thetelescope of FIG. 14;

FIG. 17 is a simplified schematic diagram of an MR sensor useful inpractice of the present invention;

DETAILED DESCRIPTION

The detailed descriptions of a fully automated telescope system withdistributed intelligence set forth below in connection with the appendeddrawings are intended only as a description of the presently preferredand illustrated embodiments of the invention, and are not intended torepresent the only form in which the present invention may beconstructed or utilized. The detailed descriptions set forth theconstruction and function of the invention as well as the sequence ofsteps utilized in the operation of the invention in connection with theillustrated embodiments. It is to be understood by those having skill inthe art, that the same or equivalent of functionality may beaccomplished by various modifications to the illustrated embodimentswithout departing from the spirit and scope of the invention.

A fully automatic telescope system with distributed intelligence and acontrol system for operating such a telescope will now be described withreference to the embodiments illustrated in the Figures.

In FIG. 1, a telescope system 10 for observing celestial, andterrestrial, objects is provided in accordance with the presentinvention. The telescope system 10 suitably comprises a telescope tube12 which houses the optical system required for resolving distantobjects and including a focusing objective and eyepiece 14 coupled tothe optical system in a manner to allow observation of the opticalsystem's focal plane. The telescope tube 12 is supported by a mount 16which facilitates movement to the telescope tube 12 about two orthogonalaxes, a substantially vertical axis, termed an azimuth axis and asubstantially horizontal axis, termed an altitude axis. As those havingskill in the art will appreciate, the horizontal and vertical axes ofthe mount 16 in combination define a gimbaled support for the telescopetube 12 enabling it to pivot in a horizontal plane defined by thevertical (or azimuth) axis and, independently, to pivot through avertical plane defined by the horizontal (altitude) axis.

It should be noted, at this point, that the telescope system 10 isillustrated as comprising a telescope tube 12 configured as arefracting-type telescope. However, the form of the telescope's opticalsystem, per se, is not particularly relevant to practice of principlesof the present invention. Thus, even though depicted as a refractor, thetelescope system 10 of the present invention is eminently suitable foruse with reflector-type telescopes. The specific optical systems usedmight be Newtonian, Schmidt-Cassegrain, Maksutov-Cassegrain, and anyother conventional reflecting or refracting optical system configuredfor telescopic use.

In the telescope system embodiment illustrated in FIG. 1, it isconvenient to support the telescope tube and mount combination in such amanner that the vertical axis 18 is, indeed, substantially vertical suchthat the telescope pivots (or rotates) about the vertical axis in aplane which is substantially horizontal. A tripod, indicated generallyat 22, conventionally functions to support the mount 16 such that theazimuth axis 18 is substantially orthogonal to a horizontal plane,relative to a user of a telescope system. The tripod 22 includes threelegs 24 a; b, c, which are arranged in a triangular pattern. Each of thelegs are independently adjustable for leveling the mount 16 regardlessof the nature of the surface on which the telescope system 10 is used.

The illustrated embodiment of the telescope system of FIG. 1 is amanual, non-automatic embodiment in that the telescope tube 12 ispivotally moved about the azimuth axis 18 and altitude axis 20 by auser's grasping and manually moving an axially mounted azimuth controlknob 26 and an axially mounted altitude control knob 28. Each of thecontrol knobs 26 and 28 are journaled to respective axis pins through aconventional gearing system such that small and precise movements of thetelescope tube 12 may be made about the azimuth and altitude axes 18 and20 by relatively large rotations of the control knobs 26 and 28. In thisrespect, the telescope system 10 of FIG. 1 resembles a conventional,manually operated telescope system.

In addition to supporting telescope motion about two orthogonal axes,the mount 16 further comprises an electrical interface junction panel 30which, in a manner to be described in greater detail below, isconfigured to support upgradeability of the telescope system 10 into afully automatic telescope system with distributed intelligence, in aplurality of logically consistent steps, each of which results in afully functional telescope system having greater or lessor degrees ofintelligence and functionality, depending on where, along the upgradespectrum, user achieves the most subjectively desirable ratio betweensystem complexity and functional benefit.

Turning now to FIG. 2, there is depicted a semi-schematic perspectiveview of the telescope system 10 of FIG. 1, including semi-intelligentmotor means for pivotally moving telescope about the azimuth axis 18 andaltitude axis 20. Semi-intelligent motor means suitably comprises asemi-intelligent, self-contained azimuth axis drive motor assembly 32and a semi-intelligent, self-contained altitude axis drive motorassembly 34. Each of the drive motor assemblies 32 and 34 areself-contained motor packages including a DC brush-type motor, anassociated electronics package hosted on a printed circuit board, areduction gear assembly and an optical encoder assembly, configuredtogether in a housing in a manner according to co-pending patentapplication entitled INTELLIGENT MOTOR MODULE FOR TELESCOPE AXIALROTATION, filed on instant date herewith and commonly owned by theAssignee of the present invention, the entire disclosure of which isexpressly incorporated herein by reference. The semi-intelligent motorassemblies 32 and 34 are each affixed to the telescope mount 16 andcoupled to the azimuth and altitude axes 18 and 20, respectively, so as,to be able to pivotally move the telescope tube 12 about thecorresponding axis when the motor assembly is activated. Each of themotor assemblies 32 and 34 are plugged into respective correspondingreceptacles in the electrical interface junction panel 30 which, in amanner to be described in greater detail below, functions as a signalinterface for the motor assemblies as well as providing power and groundthereto. The electrical interface junction panel 30 allows motor controlsignals to be directed to each of the motor assemblies 32 and 34, themotor control signals providing speed and direction information to theelectronics package which, in turn, provides appropriate activationsignals to the respective DC motor comprising the assembly. Theelectrical interface junction panel 30 further allows for signalcommunication between each respective one of the motor assemblies 32 and34 and a hand-held system control unit 36.

In operation, a user plugs the hand-held system control unit 36 into anappropriate receptacle of the electrical interface junction panel 30 andfurther plugs the motor assemblies 32 and 34 into their respectivereceptacles, thus completing a signal path between each of motorassemblies and the system control unit 36. Motion commands are providedto the system by the user by accessing the appropriate function providedon the system control unit 36. Signals corresponding to the desiredmotion are directed by the control unit 36 to the appropriate motorassembly through the electrical interface junction panel 30. Forexample, if a user desires to slew the telescope in a counter-clockwisedirection, he may enter a command into the control unit 36 telling thetelescope system to move “left”. In response, the azimuth axis motorassembly 32 is commanded to activate its integral motor to rotate in aparticular direction, thus causing the telescope mount to pivot in acounter-clockwise fashion about the azimuth axis 18. In like manner,when a user desires to elevate the telescope tube 12 in an upwardlydirection, the user would enter the appropriate “up” command into thecontrol unit 36, thus activating the altitude motor assembly 34, which,in turn, causes the telescope to pivot upwardly about the altitude axis20.

Turning briefly now to FIGS. 3 a and 3 b, the mechanical and electricalconfiguration of the electrical interface junction panel 30 areillustrated. As can be understood from FIG. 3 a, the interface junctionpanel 30 suitably comprises four RJ11-type connector receptacles, withthree of the receptacles 38, 40 and 42, comprising 4-pin RJ11 connectorsand one of the receptacles 44, comprising an 8-pin RJ11 connector. Inaddition to the RJ11 connections, the electrical interface junctionpanel includes a “mini pin” type 12 volt power receptacle 46 and avisible “power present” indicator comprising an LED 48 mounted to shinethrough a recessed opening in the panel located proximate to the powerpin 46.

FIG. 3 b illustrates the electrical connections-made between and amongthe 4-pin RJ11 connectors, the 8-pin RJ11 connector and the 12 voltpower pin 46. External power is supplied to the various connectorscomprising the electrical interface panel 30 by a suitable 12 volt powersource 48 which might comprise a dedicated 12 volt battery pack or,alternatively, an adaptor configured to mate with a 12 volt automotivebattery through, for example, an accessory power plug or a cigarettelighter. The external power source 48 is plugged into the 12 volt powerpin 46 which takes the 12 volt potential from the pin's center post anddistributes it to pin 1 of the 8-pin RJ11 connector 44 and the No. 4 pinof each of the 4-pin RJ11 connectors 38, 40 and 42. The 12 voltpotential is referenced to a return or ground potential, contacting asleeve surrounding the center post, in conventional fashion, and thereference potential is directed to the No. 8 pin of the 8-pin RJ11connector 44 and the No. 1 pin of the 4-pin RJ11 connectors 38, 40 and42. In addition, the 12 volt supply is dropped across aseries-configured resistor 50 and LED diode 48 combination such that theLED 48 emits when a power supply is present. Thus, a user is able todetermine if the system is powered-up by examining the LED 48 disposedin the recessed opening 48 in the electrical interface junction panel.

In addition to power and ground, each of the 4-pin RJ11 connectors 38,40 and 42 further comprise a 2-conductor serial signal path with pin No.3 of each of the connectors identified to a serial signal termed “CLK”and pin No. 2 of each of the connectors identified to a serial signaltermed “DATA”. A first 4-pin RJ11 connector 38 is configured as aconnector for supporting various pieces of auxiliary equipment and itsserial signal lines are each identified as “AUX”. The CLK and DATAsignals comprising pins 3 and 2, respectively, are identified as AUX CLKand AUX DATA respectively. Likewise, the next 4-pin RJ11 connector 40 isconfigured to provide serial CLK and DATA signals to the altitude motorassembly 34 (alternatively a declination motor assembly) and its CLK andDATA signal lines are thus denoted ALT CLK (Dec CLK) and ALT DATA (DecDATA) respectively. 4-pin RJ11 connector 42 is configured to provideserial CLK and DATA signals to the azimuth motor assembly 32(alternatively a right ascension motor assembly) and its CLK and DATAsignals are referred to respectively as AZ CLK (RA CLK) and AZ DATA (RADATA).

Each of the respective CLK and DATA signals of each of the respective4-pin RJ11 connectors are electrically connected to a corresponding CLKand DATA signal pin of the 8-pin RJ11 connector 44. Thus, the AZ CLK andAZ DATA signal pins of connector 42 are coupled to pin 6 and 7,respectively of the 8-pin RJ11 connector. ALT CLK and ALT DATA areconnected to pins 4 and 5, respectively, of connector 44 and AUX CLK andAUX DATA are connected, respectively, to pins 2 and 3 of connector 44.The source of each of these signals suitably comprises the hand-heldcontrol unit 36 which provides such signals over a flexible 8 conductorcable terminating in a male 8-pin RJ11 connector suitable for matingwith the 8-pin connector 44 disposed on the electrical interfacejunction panel 30.

Thus, it will be understood, that the electrical interface junctionpanel 30 provides a means for routing power and control signals betweenand among an external power source and a control unit, a plurality ofseparately provided motor assemblies and various optional auxiliarypieces of electronic equipment, such as electronic focusers, electronicleveling means, a global positioning system receiver, and the like, solong as the auxiliary electronic equipment is configured to communicateover a 2 conductor signal bus supporting clock and data signals.

The interface panel 30 can be viewed as essential distribution axiswhich enables interconnection between and among the various componentsof the automated telescope system through 2-conductor serial busconnections. Each 2-conductor serial bus carries packetized command anddata signals on one wire and clock signals on the other. Each serial busis coupled between an intelligent or semi-intelligent signal source,such as a system control unit (36 of FIG. 2) and either an axial drivemotor assembly or an auxiliary apparatus. The 2-conductor serial cablingbetween and among the different components of the system is an importantfeature of the present invention, since it allows the components to beinterconnected using small, thin, flexible cabling which is adapted forserial communication using a packet protocol. Commands and data arepassed from device-to-device in “bite sized” packets which merely informthe receiving device of the commands which the device is to execute.Large, thick, byte-wide cabling, conventionally comprising a largenumber of conductors suitable for both address and data busrequirements, are no longer required in an intelligent telescope systemaccording to the invention. Each of the novel components are suitablysized and provided with a suitable degree of intelligence so as to bequickly and simply coupled together with flexible serial interfacecables in order to realize the benefits of the system as a whole.

It bears mentioning that the use of small, thin, flexible serialinterconnect cabling significantly reduces the inertial drag on a systemthat would normally be present when using conventional multipleconductor cabling. In addition, the use of small, thin, flexible cablesvastly reduces the spring tension that conventional motor and cablesystems would apply to a telescope mount.

Pertinent to practice of principles of the present invention is thedegree of intelligence which is provided to the motor assemblycomprising either the azimuth or altitude axis motor assemblies 32 and34 of FIG. 2. Referring now to FIGS. 4 a and 4 b, the intelligence ofeither of the motor assemblies is implemented in electronic circuitry 50hosted on a printed circuit board which is disposed within the motorassembly housing along with at least a motor 52 and an optical encodersubsystem 54. The electronic circuitry 50 communicates with the outsideworld over a serial interface bus which is coupled to the circuitrythrough a 4-pin connector 56. The connector 56 is adapted to be cableconnected to a control source through either the altitude motor RJ11connector 40 or the azimuth motor RJ11 connector 42 as described inconnection with the interface panel 30 of FIGS. 3 a and 3 b. Power andground is taken from pins 1 and 4, respectively, of the connector 56 androuted to a power supply distribution circuit 58 wherein battery poweris filtered and regulated to a nominal voltage level required by thecircuitry, before being distributed to the active components comprisingthe circuit package 50. Additionally, the raw battery voltage isfiltered and provided to motor driver circuitry 51 as well as to therespective motor 52. Power distribution circuit 58, thus is able toprovide both regulated low voltages appropriate for an electroniccircuit, and filtered high voltages suitable for motor applications. Itshould be understood that while 12 Volts is preferred as a batterysupply voltage, the battery need not be limited thereto. So long as themotor and its associated driver circuitry are capable of operating athigher voltage levels, voltages as high as 16–18 Volts might be used.

The CLK and DATA lines of the serial interface are connected torespective inputs of a microprocessor 60 which functionally controlsoperation of its associated motor 52 under firmware program control.Microprocessor 60 is suitably implemented as an 8-bit microprocessor orcontroller, exemplified by the PIC16C54 microprocessor, manufactured andsold by Microchip Technology, Inc., and functions to control bothdirection of motion and speed of motion of its respective motor 52 byevaluating specific motor motion commands against a feedback signalprovided by an optical encoder assembly 54.

Although the PIC16C54 is described as a microprocessor, it istechnically an 8-bit, fully static, EPROM/ROM-based CMOS microcontrolleremploying a RISC architecture with 33 single word/single cycleinstructions. The PIC16C54 uses a Harvard architecture in which programinstructions and data are accessed on separate buses, thus improvingbandwidth over traditional von Neumann architectures where programinstructions and data are fetched on the same bus. The PIC16C54comprises a 512×12 instruction EPROM/ROM memory for hosting anoperational program instruction set and a 25 byte general purpose SRAMregister file memory. Separating the program and data memory allowsinstructions to be sized differently than the 8-bit wide data byte.Instruction opcodes are 12-bits wide making it possible to have allinstructions be single word-type instructions.

Conventionally, the PIC16C54 comprises three I/O ports, a 4-bit I/Oregister, termed port A and identified as pins A0 through A3, an 8-bitI/O register termed port B and identified as pins B0 through B7, and an8-bit I/O general purpose register termed port C and identified as pinsC0 through C7. All ports may be used for both input and outputoperation. Each of the I/O pins are tri-state, and can be programmedindividually as either an input or an output.

As depicted in FIG. 4 b, serial CLK and DATA inputs are directed to thebit-0 (A0) and bit-1 (A1) pins of the microcontroller's A port,respectively. Further, the bit-2 (A2) and bit-3 (A3) pins of themicrocontroller 60 define the motor motion control outputs and aredirected to the motor driver circuit 51 and thence to the circuit'sassociated motor 52 in order to define the scope of motor movement andits direction. As will be described in greater detail below, the I/Opins B0–B7 of port B of the microcontroller 60 are programmed to receivefeedback signals provided by an optical encoder assembly 54 which areprocessed in accordance with an application firmware program in order todefine encoder and, thus motor position. Clock input and output pins(OSC1 and OSC2, respectively) are connected to a crystal oscillator 61,operating at four times the instruction cycle rate, or 20 MHz, and whichdefines the timing reference signals for the microcontroller 60.

Commands are provided in serial fashion to the data input Al of themicrocontroller 60 in accordance with a packet communication protocol,with each command packet comprising one or more bytes of information andwith each information byte being sequentially clocked into themicroprocessor 60, bit-by-bit, by a clock signal provided to themicroprocessor's CLK pin A0. As will be understood by those familiarwith the PIC16C45 I/O, data transmission is bi-directional, while clocksignals are commonly sourced by a bus master device, such as a controlunit, as will be described presently.

Exemplary commands that are received and processed by the microprocessor60 include motor motion commands, more properly termed “step rate”commands, by which the microcontroller is instructed how fast, in whichdirection, and to what extent to move its associated motor. Since eachmotor is feedback controlled, feedback information, corresponding toactual motor movement, is stored in an “error count” register, internalto the microcontroller 60, whence it is available and may be read out toa follow-on processor for evaluation. Further commands that may beprocessed by the microcontroller 60 include commands for writing errorcount data to the register and reading microcontroller statusinformation, including motor PWM count and the change in motor positionsince the last status read operation.

Other commands that are supported by the particular microcontroller 60of the illustrated embodiment, include commands related to various powersaving features commonly implemented in modern integrated circuits. Inparticular, a SLEEP command places the microcontroller in a “sleep” modethat terminates when the interface clock signal is next driven low. Whenin “sleep” mode, the watchdog timer, if enabled, will be cleared and thedevice's oscillator driver will be turned off. The I/O ports maintainthe status they were in before the SLEEP instruction was executed, i.e.,driving high, driving low, or hi-impedance (tri-state).

Upon receipt of a motor motion (or step rate) command, indicating thatthe electronic circuitry 50 is to command motor movement, operationalfirmware in the microcontroller 60 causes appropriate PWM signals to beprovided to its corresponding motor driver circuitry and thence to themotor 52, at the appropriate pulse rate and duty cycle. The motor 52moves in response to its motion command; the extent, direction and speedof which are evaluated by an optical encoder system 54 which providesmotor positional feedback information in a closed-loop fashion.

In conventional, or classical, closed-loop control systems used inconnection with automated telescope control, one or more positionfeedback sensors may be placed anywhere between the motor shaft and thetelescope focal plane. Once a position feedback sensor is calibratedsuch that its output can be converted to an apparent stellar position,the sensor will automatically correct, through this calibration, for anysystematic errors from the motor shaft up to the position feedbacksensor.

In the particular embodiment of the present invention, the opticalencoder assembly 54 comprises a disk 55 (best seen in FIG. 4 a) aboutwhose circumference a pattern of alternating transparent and opaqueslots are disposed which, when rotated through the path of a lightsource and photodetector, are able to generate a series of pulses. Theoptical encoder disk is coupled to the shaft of a drive motor 52 in amanner as described in co-pending application entitled INTELLIGENT MOTORMODULE FOR TELESCOPE AXIAL ROTATION, commonly owned by the Assignee ofthe present invention, the entire disclosure of which is expresslyincorporated herein by reference. Since the motor 52 is coupled to itscorresponding telescope axis by means of gears (cog and worm) there isno need to take drive train slippage into account as would be the casewhen using belts or friction transfer clutches. Accordingly, the opticalencoder disk is able to be coupled directly to the motor shaft and stillprovide position information with sufficient accuracy to enable preciseacquisition and tracking of stellar objects.

The optical encoder wheel 55 is disposed with respect to the motorcircuit's circuit board such that its alternating teeth (or slots) arerotated through the path of a light source developed by an LED diode 62and a pair of bipolar photodetector transistors 63 and 64. A pair ofphotodetector transistors is used in the illustrated embodiment of theinvention in order to resolve incremental motor shaft angulardisplacement in quadrature. Thus, it will be understood that the encodersystem according to the present invention is an incremental encodersystem, as opposed to an absolute encoder system wherein the opticalencoder disk patterns are defined by either binary or Gray codes.

Pulses, for each incremental resolved motor shaft angle step, arecounted by the microcontroller 60 and the total encoder count value,representing full motion of the telescope about the axis, is evaluatedagainst the movement extent command given to the corresponding motor.Accordingly, it can be seen that if a particular motor were commanded torotate the telescope through fifty one seconds of arc in a positive(upwardly) direction, the microcontroller 60 is able to evaluate theoptical encoder system 54 to determine that the motor did, indeed, moveprecisely that amount, no more and no less. If the measured motor motionwere inconsistent with the commanded motor motion, the microcontroller60 is able to calculate the direction and extend of a subsequent motorcommand to move the motor (and thus the telescope) to its desiredposition.

The operation of the encoder system 54 will now be described inconnection with the waveform diagrams of FIGS. 7 a, 7 b and 7 c. Inaddition, it will be evident to those having skill in the art that theseparation distance between the circumferentially disposed teeth of theoptical encoder wheel 55 is mapped to the linear displacement distanceseparating the photodetector transistors 63 and 64, such that as theoptical encoder wheel is rotated before the photodetectors, eachrespective photodetector will define a periodic output signalrepresenting increasing and decreasing brightness of a light sourceemitted by the LED diode 62. It should be further noted that theperiodic signals are 90° out-of-phase so as to define a signal inquadrature.

The most desirable signal characteristics, albeit not realizable in thephysical world, are depicted in the waveform diagram of FIG. 7 a. Theoutput signal from each of the photodetectors is illustrated as asquarewave with a 50% duty cycle, with the output signal fromphotodetector No. 2 being 90° behind the output signal fromphotodetector No. 1. Evaluating both of the output signals incombination, it will be evident that there are four separatecombinations values for the signals, with the four combinationsrepeating in time in a periodic fashion. The four possible combinationsof signal values are: on-off, on-on, off-on and off-off. Because thesignal combinations appear in a particular, predetermined pattern, thedirection of motion of the encoder wheel 55 and, thus, the motor, can bedetermined by evaluating the development of the patterns. For example,for a given on-off initial phase state, if the pattern transitions to anon-on phase state, the motor is moving in a forward direction. If theon-off phase state transitions to an off-off phase state, the motor ismoving in the opposite (presumably) backward, direction. Further, eachphase state transition defines what is termed herein a “tick” anddefines ¼ of the angular rotation required to rotate the encoder wheel55 from a first tooth to the next tooth (1 period).

The definition of “on” and “off” is predicated on a photodetector outputsignal passing between two pre-set threshold voltages. As seen in FIG. 7b, each photodetector output signal defines a periodic waveform, which,in a manner to be described in greater detail below, is adjusted tooscillate within a particular voltage envelope. In accordance withpractice of the invention, each photodetector signal is defined to be inthe “on” state when its voltage excursion reaches and exceeds a 2.0 voltthreshold level. Each photodetector remains in the “on” state until itssignal level drops to a value of approximately 0.8 volts, whence thephotodetector output is deemed to switch from the “on” to the “off”state. The photodetector remains in the “off” state until its voltagevalue again reaches the 2.0 volt threshold level, whence it switches tothe “on” state. Accordingly, it can be seen that each of the signalsfrom the respective photodetectors define alternating “on” periods and“off” periods so as to define quadrature patterns.

In FIG. 7 c, the periodic signals from the two photodetectors of FIG. 7b, have been superposed, so as to define the quadrature pattern: on-off,on-on, off-on and off-off.

Returning to FIG. 4 b, the photodetector transistor 63 and 64 arepreferably implemented as MPN transistors with their collector terminalsconnected in common to V_(cc) and their respective emitter terminalscoupled to I/O pins B0 and B1 of the microcontroller 60. Themicrocontroller is thus able to count each of the quadrature ticks andevaluate the quadrature pattern so as to determine both motor speed andmotor direction by evaluating each photodetector's output. As regardsmotor movement commands, the microcontroller 60 is configured to providePWM signals to the motor driver 51 which, in turn, supplies appropriatemotor rotation signals to its associated motor 52. The microcontroller60 outputs PWM signals (pulses) at a 150 pulse per second repetitionrate and determines actual motor speed by varying the duty cycle of eachpulse. For example, to run the motor at its maximum speed, the dutycycle for each pulse would be set to approximately 99%, i.e.,substantially always on, and the repetition rate set at the maximum 150pulses per second rep rate. In contrast, were the microcontroller 60commanded to run the motor 52 at a sidereal rate, the microcontroller 60would issue PWM pulses to the motor driver 51 having an approximately 2%duty cycle and at a substantially slower repetition rate. In thisregard, it should be noted that when running at the sidereal rate, thePWM pulse rate should equal or exceed approximately 45 pulses per secondin order that the resulting telescope motion not be apparently jerky tothe human eye. It has been established that step-wise motion atrepetition rates exceeding 45 repetitions per second appears smooth andcontinuous to the human eye. Thus, PWM pulse rates should meet or exceedthis 45 pulse per second repetition rate and the motor mechanicalgearing system adjusted accordingly. Given the maximum PWM pulse rate of150 pulses per second, it will be understood that the maximum pulserepetition rate defines a minimum time window between like pulsetransition edges of approximately 6 milliseconds. In order to determinemotor speed, the microcontroller 60 counts the number of “ticks” itreceives from the optical encoder system within the 6 millisecond timingwindow. The microcontroller evaluates the number of ticks received inthe window against the number of ticks expected and, if the number ofticks received is greater than or less than the number of ticksexpected, establishes an error count in an internal register. Themicrocontroller then adjusts the motor pulse duty cycle in order toslow-down or speed-up the motor in response to the magnitude and sign ofthe error count. The resulting ticks are again compared to a nominalestablished value, with excess ticks being added to the error countregister and the shortfall being subtracted therefrom. The processcontinues until the error register is substantially zeroed-out, meaningthat the motor is now running at its expected rate. In addition toevaluating motor speed, the microcontroller 60 further stores the numberof “ticks” it has commanded the motor to move during the entire motormovement operation in a separate internal register. Thus, from thebeginning of a motor movement command to the end, the microcontrollermaintains a record of the total number of ticks the motor has movedthrough. This internal register is available for periodic interrogationby a separate control unit which, in a manner to be described furtherbelow, can translate the tick count into telescope angular displacementabout an axis and, thus, the position vector of the telescope system.

In addition to commanding motor movement and evaluating optical encoderfeedback signals, the microcontroller 60 may maintain the last-commandedmotor motion in a data field defined in RAM memory. This last-commandedmotor motion (the delta from the next-most previous motor motioncommand) is maintained in RAM and is also available for access by asystem controller by providing the appropriate memory access command tothe microcontroller 60. Thus, the motor control electronics comprisingthe electronics package 50 of the present invention can be seen tocomprise means for acquiring, storing and recalling motor positioninformation of its corresponding motor and, thus, the position of thetelescope with respect to the corresponding axis.

An additional feature of the motor control circuitry comprising theelectronics package 50 is its ability to intelligently evaluate thecorrespondence between a motor movement command and actual motor motionas read from the optical encoder system 54. In particular, themicrocontroller 60 includes firmware that evaluates a motor PWM pulseagainst ticks received from the optical encoder system 54 in order todetermine that the motor is, indeed, moving. A PWM threshold is setwithin the firmware'such that if the PWM threshold is reached withoutthe microcontroller's having received any corresponding motion ticksfrom the optical encoder system, the motor is deemed “locked” or“burnt-out” and the microcontroller ceases to issue any further motioncommands until reset. Thus, it will be seen that the circuitrycomprising the electronics package 50 includes means allowing for anintelligent evaluation of motor PWM commands versus encoder movementresponse metrics in order to determine possible motor lock or burn-out.

An additional feature implemented in the exemplary electronics package50 is an ability to adaptively tune the brightness of the opticalencoder LED diode 62 in order to provide for optimal squareness andamplitude characteristics of the photodetector signal received by themicrocontroller 60. Specifically, LED brightness is adaptively tuned byswitching one or more of five parallel-connected resistors into the LEDcurrent path between V_(cc) and a microcontroller input. Five resistors,65 a through 65 f, are parallel-connected in common to the LED diode 62at one end. The other end of each of the resistors, 65 a–65 f, areconnected to respective I/O pins (B2 through B7) comprising the B portof the microcontroller 60. One or more of the resistors are selectivelyincorporated into the LED circuit by selecting their respective I/O pinsas active.

LED brightness is considered optimized when a particular photodetectoroutput signal is evaluated as “on” approximately 50% of the time and“off” approximately 50% of the time. This condition obtains when theamplitude of each photodetector signal is such that it at least exceedsthe 2.0 volt threshold and is not sufficiently strong that it “bleeds”over the 0.8 volt “off” threshold. In other words, if the signalamplitude is too low, the photodetector is not able to “turn on”.Conversely, if the signal amplitude is too high, i.e., the signal issaturated, the photodetector will not be able to “turn off”.

LED brightness is optimized by a firmware routine that is invoked duringan initialization procedure when the telescope system is started-up.Specifically, as depicted in the flow diagram of FIG. 8, themicrocontroller 60 first causes its associated motor to spin-up and moveat a pre-determined speed in a pre-determined direction, for apre-determined period of time. During this period, the microcontroller60 evaluates the output of a single one of the photodetectors anddetermines the effective duty cycle of the photodetector output signal.

If the perceived signal duty cycle was such that the photodetector is“on” for a longer period of time than it is “off”, the microcontrollerconcludes that LED brightness is greater than a desired, nominal value.In contrast, if the effective signal duty cycle is such that thephotodetector is “off” for a longer period of time than it is “on”, themicrocontroller concludes that LED brightness is lower than its desired,nominal value. In response, resistors 65 a through 65 f are selectivelyenabled into the LED circuit. Following each resistor reconfiguration,the microcontroller again evaluates the effective duty cycle ofphotodetector signal until the effective duty cycle reaches the desired50% point. Once the desired LED brightness characteristic has beenachieved, the microcontroller 60 reviews the register statecorresponding to the B2 through B7 inputs. The register state for eachpin will have a particular value depending on whether the I/O for thatpin is active, inactive or tri-state. The register state defining thepin activation configurations required to return the necessary detectoroutput characteristics is passed, as an initialization I/O configurationvalue to an external system controller where it is stored innon-volatile memory for future reference. Alternatively, the I/Oconfiguration of the microcontroller required to return the necessarydetector output characteristics might be saved into themicrocontroller's REM memory as an I/O configuration value from where itmight be retrieved upon interrogation by an external system controller.Regardless of how saved and where it eventually resides, the I/Oconfiguration value is available to be passed to the motormicrocontroller each time the telescope system is initialized. The I/Oconfiguration value need only be obtained once, when the telescopesystem is first set up for use. The I/O configuration may, however, bereobtained and/or recalculated upon a user's initiative, in order toaccount for the gradual roll-off in LED output strength over longperiods of time. This would be useful to -observers who use theirtelescope systems on an almost continuous basis and who require thegreatest precision in automatic motor control performance.

Thus, it will be understood that the microcontroller 60, in combinationwith resistors 65 a through 65 f, the LED diode 62 and photodetectortransistors 63 and 64, comprise means for adaptively tunning LEDbrightness characteristics in order to obtain optimal photodetectoroutput signal squareness and amplitude characteristics. Optimal outputsignal characteristics are an important feature of the present inventionsince it enables motor speed and direction evaluations to be made with asignificantly greater degree of precision and accuracy than withconventional systems.

One particular embodiment of a hand-held control unit suitable for usein combination with a semi-intelligent motor assembly is depicted inFIGS. 5 a and 5 b. FIG. 5 a is a front view of the exterior portion of asemi-intelligent drive motor motion control unit 70 illustrating thevarious function keys that might be used by a user of the telescopesystem in order to command a telescope to move through variousevolutions. The motion control unit 70 comprises a hand-held,self-contained, computer control unit, enclosed within a functionalhousing. The motion control unit is operational as a dual-axis motordrive corrector which enables telescope axis motor motion, from the verysmall tracking corrections necessary for long exposure astrophotographyat sidereal rates to the very fast slewing movements required for newobject acquisition. The motion control unit supports motor movementcommands for microslewing a telescope to, and for precision centering ofa telescope onto, selected celestial objects. In addition, the motioncontrol unit 70 is able to command certain special movement functionssuch as selecting various drive rates for the telescope motors,adjusting an optional electronic focuser, and the like.

Direction keys, labeled with directional arrows indicating movementdirections (up, down, left and right) enable a telescope system to move,or microslew, in the specified direction at any one of a plurality ofallowable, settable speeds. A speed key 72 is used to change a speed atwhich the telescope system is moved by depressing the key at the sametime that one of the direction keys is being depressed. As was describedpreviously, the number of allowable speeds which can be commanded to asemi-intelligent motor assembly according to the invention, is limitedonly by the number of speed bits comprising the speed and directioncommand. In the particular embodiment being described, the number ofsettable speeds that can be commanded to the semi-intelligent motorassembly is arbitrarily limited to four. At this juncture, it isimportant to mention that these settable speeds refer to telescopemovement commanded by an observer that interrupts nominal telescopetracking motions, conducted at the well understood sidereal rate.

The four speeds selected for implementation in the illustratedembodiment range from the top speed of telescope motion, to a speedslightly in excess of the sidereal rate. The top speed corresponds totelescope displacement of from about 4° to about 9° per second. Topspeed is particularly useful for slewing the telescope to the vicinityof new object which an observer desires to acquire. A second speedcorresponds to about 0.75° per second of telescope motion and is usefulfor centering a selected object in a wide-field eyepiece. A third speedcorresponds to about 32× the sidereal rate (about 8′ of arc per second)and is useful for centering a selected object in a high-power eyepiece.The slowest settable speed is about 4× the sidereal rate (about 30′ ofarc per second and is typically used for precision centering and forguiding the telescope system during astrophotography.

Each of the individually selectable speeds are associated with acorresponding speed indicator LED which illuminates when that particularspeed has been selected. For example, a first LED 74 illuminates whenthe selected speed is the top, a second LED 76 illuminates when theselected speed is the 0.75° per second rate, the third LED 78illuminates when the selected speed is 32× the sidereal rate and thefourth LED 80 illuminates when the selected speed is 4× the siderealrate. Thus, the currently selected speed is indicated by the speedindicator LED proximate the speed key 72 and depressing the speed key 72increments the selected speed to the next speed, illuminating theappropriate speed indicator LED.

Focus control keys 82 and 84 are provided to enable the motion controlunit 70 to control the operation of an optional electronic focuser whichmay be coupled to the focusing ring of a telescope view finder. Imagesappearing in the view finder may be focused by depressing the in 82 orout 84 focus keys, causing a “DIRECTION AND MOVE” command to be issuedto an auxiliary focusing device over an auxiliary bus system, in amanner to be described in greater detail below.

A “mode” key 86 may be used to define certain special functionoperations, such as tracking rate changes, direction reversal, mountconfiguration identification, and the like. For each mode functioncapable of definition by the system, the LED bank indicates which of thechosen mode functions are operative at any given time. For example, whenpower is first applied to the motor control unit, all four LEDs arecaused to blink rapidly, indicating the unit is ready for operation.Depressing any key on the housing causes the first LED 74 to becomesteady, while the remaining LEDs turn off.

In order to select mount configuration (Alt-Az or equatorial), the userdepresses and holds the mode key 86 until both the first and second LEDs74 and 76 burn steady, while the third and fourth LEDs 78 and 80 returnto blinking. This action places the motor control unit in Alt-Az mode.To set the system into equatorial mode, the speed key 72 is depressedonce for Southern Hemisphere operation, and twice for NorthernHemisphere operation. Depressing the speed key a third time returns thesystem to Alt-Az mode. Following the mount configuration mode choice,the user depresses the mode key 86 until only the first LED 74 is lit.The unit then exits the mode function and activates the direction keys.If equatorial mode was chosen, the drive motors are now set to trackobjects at the sidereal rate.

The tracking rate of a telescope system may also be changed, in 0.5%increments from the default sidereal rate, by accessing a tracking speedmode function through the mode key 86. To do so, a user depresses themode key until the mode function shows active on the LED bank (LEDs 74and 76 “on” steady, LEDs 78 and 80 indicating the tracking mode lastchosen). Depressing the “in” key 82 causes the tracking rate to increaseby 0.5% and causes the fourth LED 80 to burn steady. Depressing the“out” key 84 causes the tracking rate to decrease by 0.5%. The third LED78 is caused to burn steady to so indicate. In order to exit thetracking rate change mode, the mode key 86 is again depressed, whichreturns the telescope to normal operation.

The internal construction of the semi-intelligent drive motor motioncontrol unit 70 is illustrated in the schematic diagram of FIG. 4 b. Ascan be seen, the operational focus of the motion control unit 70 is anEPROM/ROM based 8-bit microcontroller 88 exemplified by the PIC16C54,manufactured and sold by Microchip Technology, Inc. The function keysdescribed above in connection with FIG. 4 a, provide inputs to themicrocontroller 88 which, in response, develops control output signalswhich are directed to an 8-pin output header 90 having a pinconfiguration which corresponds to the 8-pin RJ11 connector (44 of FIG.3 b) of the electrical interface junction panel, to which the motioncontrol unit 70 is intended to be connected. In response to the variousdirection, speed, focus and mode commands input to the microcontroller88, the microcontroller develops and outputs control signals for thealtitude motor (ALT CLK and ALT DATA), the azimuth motor (AZ CLK and AZDATA), and a control signal pair for the auxiliary bus (AUX CLK and AUXDATA). Movement, speed, focus and mode commands are received by themicrocontroller 88 and appropriate output control signals are developedthereby in accordance with a software or firmware program hosted by themicrocontroller 88 and conventionally stored in an internal memory spacesuch as a programmable ROM memory.

In addition to direction, speed, focus and mode commands,microcontroller 88 is adapted to differentiate between Northern andSouthern hemisphere operations and between equatorial/Alt-Az trackingmodes. A pair of jumpers are provided, with the first jumper 92differentiating between Northern and Southern hemisphere operations byits presence or absence, respectively. Southern hemisphere operation isdefined by the presence of a jumper in the first jumper position 92which completes the electrical short and asserts an I/O active state onboth the RTCC and B6 inputs. For Northern hemisphere operations, thejumper is absent from the first jumper position 92 putting the RTCCinput in an I/O inactive state.

Likewise, equatorial and Alt-Az operational modes are differentiated bythe presence or absence of a jumper in the second jumper position 94,respectively. Alt-Az mode is defined by shorting the jumper position andthereby asserting an I/O active state on the RTCC and RBC inputs.Equatorial mode is indicated by an I/O inactive state on RTCC while theB7 input remains active.

With regard to communication between microcontroller 88 of the controlunit and the microcontroller 60 of the semi-intelligent motor assembly,commands are provided in serial fashion to the semi-intelligent motorassembly in accordance with a packet communication protocol, whereineach command packet comprises one or more bytes of information and witheach information byte being sequentially clocked into the receivingmicrocontroller, bit-by-bit, by a serial clock signal. In accordancewith practice of principles of the invention, each semi-intelligentmotor assembly is directly coupled to the control unit's microcontroller88 via a two-wire serial interface connection through the control unit'sheader 90 and, thence to appropriate I/O pins of the microcontroller 88.Thus, information being communicated between a control unit and a motorassembly need not be preceded with header information. However, sincethe auxiliary serial interface is able to host a multiplicity ofauxiliary apparatus, information being communicated between a controlunit's microcontroller 88 and a particular piece of auxiliary apparatusneeds to be preceded by an address header in order to identify theinformation's intended recipient.

With regard to motor motion commands, these commands are issued directlyto the motor assembly's microcontroller over the corresponding two-wireserial interface. Motor motion commands, more correctly termed step ratecommands, are identified, in hexadecimal, as (00h) and comprise threebytes of information. The step rate is defined as the number of steps or“ticks” that occur approximately every 6 milliseconds. The format is atwo's compliment number with the first number representing the wholesteps or “ticks” and the next two bytes representing the fractionalportion thereof. Each step rate command includes a sign (+/−) whichdetermines the direction of motor motion.

A second step rate command, denoted (01h) in hexadecimal is formattedsubstantially identically with the (00h) command but is used for steprates greater than the 2× the sidereal rate. Additional informationcommunicated between the control unit microcontroller and the motorassembly microcontroller include a “change error count” command (02h)which commands a one time change of the motor microcontroller errorcount register. A “set LED position” (03h) command sends out the I/Oconfiguration byte which has been stored for that particular motorassembly in order to optimize its photodetector performance. A “find LEDposition” (04h) command is issued to the motor assembly when it isdesired that the motor assembly finds the best LED current in order tooptimize photo detector performance. A “get LED position” (09h) commandinstructs the motor assembly to write out the I/O configuration bytethat corresponds to optimized photo detector performance.

Additional commands, such as “turn on motor in positive direction” (06h)and “turn on motor in negative direction” (07h) are also provided by thecontrol unit to the motor assembly's microcontroller. A “status” (08h)command is read from the motor assembly's microcontroller the “status”command is typically 3 bytes in length and further includes anadditional flag bit. The first two bytes of information comprise thedetermined change in motor position since the last status read. The nextbyte comprises the PWM pulse count which is used to determine whether ornot the motor is in a stall condition. The final bit, the flag bit, anillegal encoder flag which indicates that an encoder “tick” was missedduring the current motor position change. This bit is typically resetafter a data read, as is the determined motor position information.

Those familiar with the internal construction and operationalprogramming of a PIC16C5X series microcontroller will be able toroutinely develop additional applications and command sets suitable for,for example, controlling LED operation, developing a digital clock, orcontrolling a keypad. All that is required in practice of principles ofthe invention, is that the control unit microcontroller be able tocommunicate with one or more motor assemblies so as to command, atleast, motor speed and direction changes which the motor assemblyexecutes without further intervention on the part of the control unit.This distribution of intelligence allows both the motor assembly and thecontrol unit to be implemented using relatively simple components, witheach respective apparatus being responsible for a particular set offunctions; the control unit translating keypad input into motor motioncommands, the motor assembly receiving the motor motion commands andcausing the required amount of telescope motion about its axis. Commandsand status information are communicated between the control unit and themotor assembly via a two-wire serial interface in accordance with apacket communication protocol. The control unit is able to determinethat its commands have been appropriately executed by evaluatingreturned status information from the motor assembly. Appropriatetelescope motion in response to a motor movement command is ensured byevaluating feedback signals developed by an optical encoder systemmechanically coupled to the motor and electronically evaluated by themotor assembly's microcontroller unit.

Thus, in accordance with the invention, the hand-held control unit andmotor assembly, in combination, suitably provide means for distributingmotor control intelligence, with the intelligence partitioned into firstand second portions, the first portion responsive to user input and fortranslating that input into suitable command signals, the second portionresponsive to the command signals and translating the command signalsinto signals suitable for use by a motor driver circuit in effectingmotor motion. The two portions of the system's distributed intelligenceare coupled together over a two-wire serial interface allowingbi-directional communication of data and command signals between the twoportions over a thin, flexible cable.

An additional embodiment of a hand-held control unit suitable forintelligent control of a telescope system according to the invention, isillustrated in FIGS. 6 a and 6 b. FIG. 6 a depicts the exterior of anintelligent telescope system controller as it would appear to a systemuser, while FIG. 6 b illustrates, in semi-schematic block diagram form,configuration of the electronic system components which providefunctionality to the controller 100.

FIG. 6 a is a front view of the exterior portion of an intelligenttelescope system controller 100 illustrating the various function keysthat are used by a user of the telescope system in order to command atelescope to move through various evolutions. The intelligent controller100 comprises a hand-held package which functions as a full-spectrumcontrol unit capable of intelligently defining and commanding motormovements required for astronomical observations, as well as forimplementing various pre and post processing features in a mannersimilar to a microcomputer.

The intelligent controller 100 suitably comprises an LCD display screen102, capable of displaying text, numeric and graphic output data thatmight be consulted by a user in operating the telescope system. Allprompts, user queries, confirmation messages, and the like, aredisplayed on the LCD screen 102. Telescope motion direction keys 112,labeled with directional arrows, indicating up, down, right and left,provide the necessary inputs for enabling the telescope system to move,or microslew, in the specified direction, at any one of a number ofallowable, settable speeds. As was described previously, the number ofallowable speeds which can be commanded to the semi-intelligent motorassembly according to the invention, is limited only by the number ofspeed bits comprising the speed and direction command. In the particularembodiment being described, the number of allowable speeds that can becommanded to the semi-intelligent motor assembly is 8, with one of the 8allowable speeds being reserved for the motor stop command. Motor speedchanges are effected by entering numerical values on a numeric keypad104. To change or define a particular motor speed, a user presses andreleases the desired numeric key corresponding to the desired speedrange (1 being the slowest, 9 being the fastest). Once the desired speedis selected, the desired motion direction key 112 is depressed and thesystem commands the corresponding semi-intelligent motor assembly tomove the telescope system at the desired speed, in the desireddirection.

Scroll keys 106 and 108 are provided in order that a user may scrollthrough a data base listing or through available menu options that mightbe shown on the LCD display screen 102. A “?” key 110, disposed betweenthe scroll keys 106 and 108, accesses an internal “help” file and, whendepressed, causes the LCD screen 102 to display a brief description ofthe selected menu item on the first line of the display. An enter key113 selects a file menu or option, or is used to define the completionof an entry made in response to a system prompt. A mode key 114 allows auser to exit a current menu to return to a previous menu and a go-to key115 commands the telescope system to slew the telescope to an objectchosen from an internal celestial object data base listing, for example.

The internal construction of the intelligent telescope system controller100 is illustrated in the schematic diagram of FIG. 6 b. As can be seenfrom the figure, the intelligent controller, indicated generally at 100,suitably comprises a dual processor system, with the dual processingfunctions implemented by a first, general purpose microprocessor 120exemplified by the 68HC11, a member of 68HCxx family of microprocessorsmanufactured and sold by Motorola, and a second, purpose configuredmicroprocessor or microcontroller 121, exemplified by the PIC16C57microcontroller manufactured and sold by Microchip Technology, Inc.

The general purpose microprocessor 121 is coupled to a 16-bit addressand data bus (AD[0,15]) and an 8-bit data bus (D[0,7]), which allow themicroprocessor 121 to communicate with a programmable read-only memory(ROM) memory circuit 124 and a random access memory (RAM) 126. Further,the four most significant bits of the data bus (D[4,7]) are coupled tothe system's LCD display driver circuit 127 to provide an interfacebetween the microprocessor 121 and the system's LCD display 120. As willbe described in greater detail below, the microprocessor 121 isresponsible for implementing the top-level firmware architecture of thesystem according to the invention and for executing loadable applicationsoftware routines pertinent to the exemplary intelligent telescopesystem.

Programmable read-only-memory circuit 124 is preferably implemented as aFLASH programmable ROM and is provided in order to host the instructionset for downloaded applications and software routines, data tables suchas a stellar object position data base, the Messier object catalog list,an earth-based latitude/longitude correspondence table, and the like.Although described as an FPROM, the ROM memory may be implemented as anEEPROM, or any other type of programmable non-volatile memory element.Indeed, the ROM 124 might be implemented as an external mass storageunit, such as a hard disk drive, a programmable CD-ROM, and the like.All that is required, is that the memory 124 be able to be written to,in order that its hosted data bases and tables may be updated, and benon-volatile, in order that its hosted data bases and tables beavailable to the system upon boot-up or power-on-reset.

Microprocessor 121 is further coupled via a 2-bit serial-type controlbus 123 to the microcontroller 122 which, in turn, is coupled via amultiplicity of interface signal lines to the various function keys(indicated generally at 132) which comprise the operator/systeminterface for this system. In this respect, the microcontroller 122functions as the system I/O and interface controller which translatesuser input taken from the keypad, and provides command and controlsignals, derived from the user input, to the system microprocessor overthe serial interface 123. The serial, interface bus 123 is furthercomprised of two signal lines, CLK and DATA, which function much thesame as the 2-wire serial interfaces between a motor assembly and theparticular embodiment of a control unit described in connection withFIG. 5 b. The interface bus 123 is bi-directional and command and datasignals are communicated in accordance with a packet transmissionprotocol.

The system microprocessor 121 is further coupled to RS-232 interfaceport circuitry 128 via an additional 2-wire (supporting conventional Txand Rx signal lines) serial bi-directional interface bus 133. The RS-232port circuitry 128 is in turn coupled to an RS-232 interface connector129, through which bi-directional communication between themicroprocessor 121 and external information sources such as a personalcomputer (PC), a World Wide Web interface link, and the like, may beeffected. Indeed, the RS-232 port 128 may be configured to communicatewith a similar RS-232 port comprising another, separate intelligentcontroller system operating in connection with another, separatetelescope system. It will be understood that, when operating underappropriate I/O control application firmware, the microprocessor 121 incombination with the RS-232 port 128 provides means for quickly andeasily interfacing the system to an external source of programming code,data or other information that a user might desire to incorporate intothe operating instructions or data tables comprising the intelligentcontroller of the present invention.

Likewise, the microcontroller 122 is coupled to a bundled serialinterface connector 130, suitably comprising an 8-pin RJ11-typeinterface suitable for connection to the 8-pin receptacle (44 of FIGS. 3a and 3 b) of the electrical interface panel (30 of FIGS. 3 a and 3 b).The serial interface connector is configured to support communicationbetween the microcontroller 122 and two telescope axis drive motorassemblies along with a plurality of auxiliary devices, over respective2-wire serial interface busses. So configured, the PIC16C57microcontroller 122 will be understood as interfacing between the userI/O interface keys 132 and the 68HC11 microprocessor 121, to generatecommand and control signals suitable for use by a semi-intelligent motorassembly and/or an auxiliary device, such as an electronic focusingsystem, and provide such command and control signals to the serialelectrical interface panel (30 of FIGS. 3 a and 3 b) for routing totheir appropriate destination. A crystal oscillator circuit 135 isfurther coupled between the microcontroller's clock inputs (OSC1 andOSC2) and provides an 8 Mhz operational clock signal to themicrocontroller 122.

Power is also received, from an external power supply, through theserial interface connector 130. The power and ground pins are coupled toa power supply circuit 134. The supply circuit 134 is preferablyimplemented as a voltage regulator and functions to condition a 12 Volt(for example) supply input to the reduced voltage levels required bymodern integrated circuits. A pertinent consideration given to the powersupply circuit 134 is its need to provide suitable supply voltages andcurrents for a plurality of LEDs which populate the system 100. Inparticular, the LCD display 120 is backlit by an arrangement of LEDswhich are configured in a circuit 136 and disposed about the displayscreen in a novel fashion to provide uniform illumination of the entiresurface of the display screen. Operation of the LED circuit 136 iscontrolled by the microcontroller 122, and its configuration will bedescribed in detail below.

In accordance with the present invention, the 68HC11 microprocessor 121performs the high level application software execution tasks and theassociated data handling and numerical processing, in order to definethe appropriate motion commands to be provided to the PIC16C57microcontroller 122. The microcontroller 122 receives motion commandinputs from either the microprocessor 121 or the user interface keysover interface bus 123 and suitably processes the received motioncommands into command and control signals suitable for use by a motioncontrol processor.

To complete the system, and to give the microprocessor 121 some means ofperforming time calculations appropriate to celestial motion, a realtime clock 138 its provided and is coupled to a clock input of themicroprocessor 121, as well as being coupled to a clock input of themicrocontroller 122. The real time clock 138 is preferably implementedas a precision timing reference clock signal generator, such as a UTCclock, that is used by the microprocessor 121 to calculate sidereal timeintervals and preferably resides as an integral component of the controlunit 100. Alternatively, the clock 138 might be implemented as aseparate, off-board integrated circuit comprising a conventional UTCclock which communicates with the system over the RS-232 interface, oran on-board UTC clock and follow-on circuitry for converting UTC timeintervals to sidereal time intervals prior to providing a timingreference signal to the microprocessor 121.

Thus, it should be understood that the intelligent telescope systemcontroller 100 suitably comprises a means for adding full intelligenceto a telescope system which includes semi-intelligent motor assembliesin accordance with the present invention. The intelligent telescopesystem controller performs this function by bifurcating the system'sprocessing and control functions into a first, sub-system comprising amicroprocessor operative for system data processing, and a second,microcontroller system for implementing I/O control. System intelligenceis maintained up-to-date, by allowing “new object” loadability throughan RS-232 port. System software, updated celestial object catalogtables, and the like, may be loaded into the system through the RS-232port from a PC, an attached disk or diskette drives a web site, aseparate intelligent telescope system controller in accordance with theinvention, and the like.

In particular, a user may “clone” his system's application programs andhis system's database contents into another user's system using theRS-232 port to effect bi-directional communication. Alternatively, theuser may receive program and data information from a second intelligenttelescope system controller, thus “cloning” that controller into hisown, over the RS-232 interface. The “clone” function is implemented byaccessing the various user interface keys provided on the exterior ofthe controller 100. For example, the user might depress the mode key 114until a system I/O menu appears in the controller's LCD display. Theuser might then scroll through the menu using the scroll keys 106 and108 until a “clone” menu option appears in the screen. If suitableconnections are made between two intelligent system controllersaccording to the invention, and if the appropriate input and outputstates are set for each controller (the controller being cloned outputsdata), the user might depress the enter key 113, initiating the process.

Several other system utilities are supported by the microprocessor 121of the intelligent telescope system controller according to theinvention. For example, the system may be placed in a state ofsuspension by invoking one of two, reduced functionality, modes termed“sleep mode” and “park mode”. Since, as was described above, the systemand timing reference is preferably a crystal controlled clock 130coupled to the microprocessor 121, an external time-of-day input isrequired in order that the system can correctly calculate the system'slocal hour angle and, thus, the celestial sphere's rotational state withrespect to a specific observer. When the system is placed in “parkmode”, all system orientation parameters (to be described subsequently)are saved in the buffer/scratch pad RAM 126, from whence they may berecalled when a user desires to perform additional observations. Oncethe system is oriented and has been placed in “park mode” all that isrequired is that the user input a time-of-day datum for the telescopesystem to precisely know (or, more correctly, remember) its orientationwith respect to the sky.

In “sleep mode” the system again remembers its orientation parameters,but maintains the clock 138 in an operative condition while reducingpower to the remaining system components to maintenance levels. Thus, in“sleep mode”, the system is ready to “wake up” at any time the usergives it an operation command.

Beyond support of system utilities, the intelligent telescope systemcontroller is also able to support a multiplicity of auxiliary devicesthat might be coupled to the telescope system in order to enhance itscapabilities. Pertinent such devices include an automatic focusing unit,a clock and date module, a speech recognition module and an associatedaudio output module, an automatic alignment tool(tube leveler and/oraxis planarizer), a global positioning system (G.P.S.) module, aphotometer, an autoguider, a reticle illuminator, a cartridge readerstation (for courseware, new revisions, new languages, object libraries,data storage) and the like. Each auxiliary device is coupled to thesystem, in daisy-chain fashion, over the AUX DATA and AUX CLK signallines comprising a serial auxiliary bus system. As was the case for theAlt (Dec) and Az (RA) serial busses coupled between the controller andthe motor assemblies, the auxiliary bus is a 2-wire serial communicationinterface and further includes a supply voltage line, supplying 6–18 andpreferably 12 Volts of power, and a ground potential line.

The 2-wire interface comprises a bi-directional data line which supportsdata communication using a packet transmission protocol, and a clockline which supports a clock signal typically sourced by the bus master,in this case, the system controller. Because the auxiliary devices aredaisy-chain configured, each device is provided with a unique busaddress so that commands can be efficiently processed by the particulardevice being accessed. In accordance with the present invention, busaddresses are expressed as a binary numerical value defining an addressbyte. Thus, the system is able to communicate with up to 256 separateaddresses and, therefore, 256 separate devices. However, as will beexplained below, one address, the “byte zero” address, is reserved as abroadcast address, indicating that the following command or commands areto be executed by all devices coupled to the bus.

All communication transactions over the auxiliary interface bus areperformed in accord with a packet transmission protocol. All busactivity begins with a bus master (typically the system controller)initiating a communication packet to a selected target device. Once themaster-to-target communication is completed, the target device returns amessage or status communication packet back to the bus master. Asillustrated in the simplified interface protocol packet content diagramof FIG. 12, all packets begin with “count byte” which defines the numberof bytes comprising that particular initiating or response packet. Inthe case of an initiating packet, the second byte comprises the “addressbyte” for the particular target device which will execute the command,and is followed by a “command byte” which defines the operation to becarried out. “Intermediate bytes”, unique to each device, follow the“command byte” in the case of an initiating packet, or the “count byte”in the case of a response packet. A “last byte” is also unique to eachdevice and is the final byte of an initiating packet transmitted by themaster. Optionally, a target device may be configured to transmit a“last byte” as the final byte of a response packet.

The clock signal is driven by the bus master for all informationtransfers, regardless of the direction of data flow. In addition, thebus master may temporarily relinquish control of the bus and designate aparticular device to temporarily assume the bus master role inthird-party data transfer operations, such as between a CCD imager and adisk drive. All auxiliary devices are “I/O hot” in that all devices areconstantly “snooping” the bus and can evaluate all packets transmittedthereon. Once a device determines that a packet header contains itsaddress, the rest of the packet is clocked into its I/O registers andthe command is then executed.

Certain broadcast commands are common to all auxiliary devices and areidentified by a “broadcast address”, indicating that all devices coupledto the bus are to execute the following command. Exemplary broadcastcommands include a “bus reset” command which is used to perform a softreset of the bus and the “sleep” command which places each device in itsown particular low-power mode. An “inquiry” command is not specificallya broadcast command, but is nevertheless directed to all devices on thebus; albeit sequentially. The “inquiry” command is used to determine thepresence of a device on the bus. The initiating packets cycle throughthe bus addresses, with devices populating the bus returning a statusbyte identifying the device revision number or module type, as theiraddresses are received.

The full spectrum of auxiliary device command sets can be easilyimplemented in the intelligent system controller (100 of FIGS. 6 a and 6b) because of the capability range of its microprocessor (121 of FIG. 6b). It will be understood, that the full spectrum command set may beincorporated in the microprocessor by a reasonably proficient programmermaking the intelligent system controller 100 capable of supporting thefull spectrum of auxiliary devices. A reduced set of auxiliary devicecommand sets are implemented in the semi-intelligent system controller(70 of FIGS. 5 a and 5 b) because of the relatively limited capabilitiesof its microcontroller 88, with respect to the capabilities of the fullyintelligent system. Thus, only certain auxiliary devices are supported,such as an electronic focusing unit, in the semi-intelligentconfiguration, while the capacity for upgrading -the system to a fullyintelligent configuration remains unimpaired. Indeed, the serialauxiliary interface bus provides a particular enabling feature forsystem upgrade capability by virtue of its simplicity and the inherentexpandability of the 2-wire serial bus concept. Adding capability to thetelescope system of the invention, is as uncomplicated as merelycoupling additional devices to the bus. The bus, then, provides theframework within which intelligence and capability are added, subtractedor modified on a piece-by-piece basis.

Each component coupled to the system comprises its own operationalintelligence and requires only a serial command interface with acontrolling entity to perform its designated function. Since eachcomponent comprises sufficient intelligence (processing power) toexecute its tasks without higher level supervision, the controllingentity is free to execute application programs, perform complexarithmetic calculations, maintain database entries, and the like.

Primary control of an automated telescope system with distributedintelligence, in accordance with the present invention, is provided by afully intelligent telescope system controller 100. Substantially allfunctions of an automated telescope system can be implemented throughthe keypad portion of the controller 100 by depressing the variousalpha, numeric and function keys provided thereon. Once the automatedtelescope system has been appropriately aligned, as will be described ingreater detail below, an object menu library, stored in a dedicatedmemory space provided in the controller, is used to automatically slewthe telescope system to any particular celestial (or terrestrial) objectan observer desires to view or photograph. However, prior to beginningan observation and, indeed, during initial setup of the system, a usermust first initialize the system by entering certain information inaccordance with an initialization, or setup, procedure which can be bestunderstood with reference to the initialization procedure flow chart ofFIG. 8.

After each of the individual components comprising the telescope systemare connected together through the electronic interface junction panel(30 of FIG. 2), the intelligent system controller 100 is plugged intothe control unit port (44 of FIGS. 3 a and 3 b) and power is provided tothe system. Following “power-on-reset”, a warning message is displayedon the LCD screen 102 of the system controller 100, warning the user notto look directly at the sun through the telescope. The warning remainson the LCD screen 102 for a period of a few seconds following which thesystem controller prompts the user to enter the current date, byentering the appropriate figures in a formatted date field. An exemplarydate field might appear as “Jan. 1, 1999”. Numeric values, such as thedate and year are entered by pressing the corresponding numeric keys ofthe numeric keypad 104 when prompted to do'so by the system. The currentmonth is entered by scrolling through a list of months using the up 106and down 108 arrow keys provided for that purpose. In particular, thedate cursor automatically jumps to the next space once a particularnumeric value is entered. If a mistake is made during entry, the rightor left directional keys may be depressed in order to move the cursorbackward or forward until it is positioned over the incorrect entry. Thecorrect entry may then be made by depressing the appropriate numeric keyon the numeric keypad 104.

The numeric keys are used to enter the current day. Then, the up 106 anddown 108 scroll keys are used to cycle through the list of months. Whenthe current month is displayed the right arrow key causes the cursor tomove to the year field into which the current year is entered using thenumeric keys 104. After all of the date information has been correctlyentered, a user depresses the enter key 113 in order to inform thesystem that the current date has been entered and the date settingprocedure is now concluded.

The system then prompts the user to enter the current time. It should benoted that the system-is operative in a 24-hour mode and, therefore,time should be entered using a 24-hour clock (i.e., 9:00 pm is enteredas 21:00). As was the case with the date entry, a user depresses theenter key 113 in order to inform the system that the time entryprocedure has been concluded. It is worth mentioning, at this point,that a user should enter a time just slightly ahead of the current timeprior to depressing the enter key. The enter key is depressed at theexact moment the current time matches the time the user entered. Thisprocedure is very useful in enhancing the precision of the positioningcalculations undertaken by the system, by giving the system a moreprecise indication of the correct time. Needless to say, the moreprecise the time indication provided to the system, the better thesystem will be able to locate objects on the basis of their publishedright ascensions and the better the system will be able to accuratelyposition the telescope to view them.

At this point, the positioning keys 112 of the system controller 100 areactivated such that they may be used to move the telescope. A user isable to either immediately proceed to using the telescope withoutfurther initialization data entry, or continue with data entry in orderto enable additional features of the inventive system. If a user choosesto continue with initialization, a next procedure displays the status ofa daylight savings time feature. Daylight savings time is in effect fromthe first Sunday in April through the last Sunday in October in mostareas of the United States and Canada. Users are cautioned toinvestigate as to whether their geographic local time conforms todaylight savings time or not. The display status is in a “negativedefault” condition indicating that the daylight savings time feature isnot enabled. If a user is currently in daylight savings time, the enter113 key is depressed once which causes the display indication to changefrom NO to YES. When the desired setting is displayed on the screen, themode 114 key is depressed indicating that the daylight savings timeprocedure is concluded.

A next sequence of data entry options enables a particularly novelorientation feature of the present invention, wherein an observer'slatitude and longitude are approximated by the latitude and longitude ofthe closest city or other geographical landmark which a user maydesignate as reasonably approximating his observation location. Forexample, the next procedural step causes the LCD display 102 to requestentry of the nation, state or province, of the user's primaryobservation site. The UP 106 and DOWN 108 scroll keys are used to scrollthrough a list of various countries, states and provinces contained inthe system's database until the observer's nation, state or provinceappears on the screen. Following selection of the observer's nation,state or province, the observer is requested to select the closest cityor major geographical feature to their primary observation location byusing the UP and DOWN scroll keys to cycle through an alphabetical listof cities and geographical features. When the desired city or feature isdisplayed on the LCD screen, the user presses the enter key 113 toinform the system that the virtual location procedure has beenconcluded. The geographical coordinates (latitude and longitude) of theselected site are then entered into system memory as a firstapproximation observation location indicia which is used in combinationwith the current time to orient and align the telescope system for fullyautomated use.

This virtual location procedure is enabled by a database tablecomprising a multiplicity of alphabetically listed geographic locationswith each associated to their known latitude and longitude coordinates,as depicted in FIG. 9. FIG. 9 illustrates a partial database listing ofan exemplary top-level location table and a sub-level database listingfor locations contained within the indicated California entry. Thelocation database listing is typically stored in the system's ROM memory124, but might alternatively be stored in an external disk drive, onfloppy diskette, or some other such mass storage device so long as thelocation database listing is stored in some form of non-volatile memorysuch that it may be accessed at need upon system power-up.

The need for such a virtual location procedure is evident when oneconsiders that the location of a particular celestial object in thenight sky, at any given time, is solely a function of the observer'slatitude and the observer's local hour angle displacement from thecelestial meridian, in turn a function of the observer's longitude andthe observer's local time-of-day. Thus, once an observer's latitude andlongitude are known, and the time-of-day (expressed in universal timecoordinates) is known, the observer has, all of the informationnecessary to compute the relative bearing in either altitude and azimuthor declination and right ascension of any celestial object whoseabsolute coordinates are known. When an observer enters a reasonableapproximation of his latitude and longitude, and enters his local time,the system is able to reasonably approximate the orientation of thenight sky with respect to that observer. As will be described in greaterdetail below, further corrections may be made to this “firstapproximation” orientation procedure in order to more precisely andaccurately define the night sky with respect to the telescope'sorientation.

Following the virtual location procedure, the system then prompts a userto enter the configuration and alignment mode to be used for thetelescope system to which the system controller 100 is coupled. Thesystem has two configuration and alignment options; Alt-Az and polar(equatorial). The choice between these two configuration and alignmentmodes is made by scrolling through the choices using the UP 106 and DOWN108 arrow keys until the appropriate configuration and alignment modeappears on the screen. When the appropriate mode appears, the userdepresses the mode 114 key thereby informing the system of theconfiguration and alignment method most appropriate for the telescopesystem. Once system configuration is determined, the controllercommences a motor test, slewing the telescope a short distancehorizontally and vertically (RA and Dec). After the motor test iscompleted, the system initialization is complete and the telescopesystem is ready to be aligned for observations.

System initialization is performed the first time that power is appliedto the system controller 100 or any time the system is affirmativelyRESET. During subsequent observation sessions, when power is applied tothe system controller 100, the controller internally initializes andwill only prompt a user to enter a randomly selected number used inconnection with the sun warning and, subsequently to enter the time anddate. From this point, the system proceeds directly to telescopealignment and, in addition, if the polar (equatorial) configuration andalignment model was specified during the initialization procedure, thesystem controller 100 automatically activates the right ascension (RAand Dec) motor subassemblies.

Since the system controller is operable to define telescope alignmentwith respect to both Alt-Az and polar (equatorial) configuration andalignment models, it would be appropriate to discuss the differentalignment procedures associated with each of the models seriatim, withthe Alt-Az alignment models being described first. In accordance withpractice of principles of the invention, the system enables the user tochoose among four different alignment procedures, three of which areconcerned with aligning the telescope to the celestial sphere and one ofwhich is used in connection with terrestrial alignment.

In a manner well understood by those having skill in the art, atelescope configured to operate in an Alt-Az mode is unable to “stop thesky” in hardware by maneuvering in equatorial coordinates. Accordingly,Alt-Az telescope configurations must “stop the sky” in software whentracking a celestial object. In contrast to a polar or equatorialmounting, which may be driven in one axis only, at a constant rate, bothaxes of an Alt-Az telescope mount must be driven at rates that vary overa wide dynamic range. Specifically, the drive rate equations for thealtitude and azimuth motors, respectively, of an Alt-Az telescopesystems are as follows:

$\begin{matrix}{\frac{\mathbb{d}Z}{\mathbb{d}h} = {15\;\sin\mspace{11mu} A\;\cos\;\varphi}} & {{EQUATION}\mspace{14mu} 1} \\{\frac{\mathbb{d}A}{\mathbb{d}h} = {{- 15}\left( \;{{\sin\mspace{11mu}\varphi} + {\cot\; Z\;\cos\; A\;\cos\;\varphi}} \right)}} & {{EQUATION}\mspace{14mu} 2}\end{matrix}$Where Z is the calculated zenith distance of an observer, h is theobserver's local hour angle (or LHA), A is azimuth (measured Westwardfrom the South) and φ is the observer's latitude. The rate of change ofan object's zenith distance Z with hour angle h and the rate of changeof an object's azimuth A with respect to hour angle h is defined inunits of (sidereal second)⁻¹. Thus, in order for the telescope system tobe able to adequately acquire and track a given celestial object, it isnecessary that the telescope system understand its orientation withrespect to the sky such that such that an observer's latitude and localhour angle (φ, h) can be calculated.

Over the centuries, a great deal of thought and consideration has beengiven to various methods for determining latitude and longitude from anevaluation of the positions of celestial objects with respect to thecelestial coordinate system. Specifically, the field of celestialnavigation is directly concerned with mathematical methods fordetermining an observer's latitude and longitude from measurements takenof the positions of the sun, moon, planets and various known stars.Although position determination methodologies have evolved over thecenturies, they may all be conceptually viewed as defining variousmathematical means for observing and measuring the positions ofcelestial references in an earth-based coordinate system (rectangularcoordinates or altitude-azimuth coordinates) and comparing themeasurements so obtained with the positions of such celestial objectsexpressed in celestial coordinates (right ascension and declination) asare tabulated in an ephemeris.

The solution to any given problem in celestial trigonometry thereforedepends on being able to convert measurements obtained in one coordinatesystem (Alt-Az, for example) in the other coordinate system (thecelestial coordinate system). Coordinate system conversions are wellunderstood by those having skill in the art and, indeed, have alsoundergone a conceptual evolution, culminating in modern day, computerassisted, matrix transformation and rotation mathematics. Nevertheless,regardless of the coordinate systems used to express an observation andthe coordinate system used to define a universal reference, observationsmade in one coordinate system may be rotated into the referencecoordinate system using simple mathematical principles, so long as twopoints in one coordinate system correspond to the same two points in theother coordinate system such that the transformation boundaries withrespect to displacement and rotation are defined. Thus, in accordancewith generally accepted mathematical principles, two reference pointsexpressed in an Alt-Az coordinate system, for example, are a necessaryand sufficient condition for the Alt-Az coordinate system to be rotatedinto a celestial coordinate system, so long as those same twomeasurement points have a corresponding location metric in the celestialcoordinate system.

Proceeding now to the alignment methodologies in accordance withpractice of the invention, a first, “easy” alignment procedure will bedescribed in connection with the procedural flow chart of FIG. 10 a.After internal initialization prior to beginning an observation session,the LCD display 102 of the intelligent telescope system controller 100displays a prompt screen requesting the user to select one of fouralignment procedures, which a user may select by scrolling through thevarious choices using the UP 106 and DOWN 108 scroll keys. A firstalignment procedure, denoted “easy” requires no knowledge of the nightsky because the system controller is able to locate its own alignmentstars based on the date and time entries provided by the user duringinitialization.

Specifically, when the “easy” alignment procedure is selected, thesystem next prompts the user to move the telescope (using the motionkeys 112) until the telescope is pointed North. After the telescope tubeis pointed North, a user depresses the enter key 113 to inform thesystem that the telescope tube is in its appropriate position. Next, thesystem prompts the user to level the telescope tube by adjusting thetelescope's altitude position until the altitude (or declination)setting circle is set to 0°. Pointing the telescope North and levelingthe telescope tube functions to zero-in the position encoders of thealtitude and azimuth motor assemblies. Any subsequent motion of thetelescope away from its 0,0 position allows the telescope system todirectly calculate its altitude and azimuth displacements from the 0,0reference point. Using the time and date entries presented by the user,the telescope system consults a database of well known celestial objectsand selects a particular bright object which is currently above thehorizon. The entered time and date information allows the system tocalculate whether that particular bright object has rotated sufficientlyin right ascension to bring it above the observer's horizon, while thevirtual latitude and longitude entry provided by an observer's enteringtheir closest city or geographic feature, provides the system withsufficient information regarding an observer's latitude so that it maycalculate an approximate declination value for that bright object.

Once an object (star) is identified in the database, the systemautomatically slews the telescope to the vicinity of that star bycommanding the appropriate motion from the altitude and azimuth motors.Once the telescope has slewed to the vicinity of the desired star, theobserver is prompted to center the star in the field of view of thetelescope eyepiece, using all four direction keys (112 of FIG. 6 a) asrequired to center the star. When the star is centered in the field ofview of the eyepiece, the observer presses the enter key 113 and thesystem then searches the data base for a second bright object or starwhich is displaced at least 30° from the previous star in order toincrease the accuracy of alignment procedure. Once the second star isidentified from the data base, the system automatically slews thetelescope to the vicinity of that star and once again prompts the userto center that star in the field of view of the eyepiece using thedirection keys 112 of the system controller 100. When the second star iscentered, the system calculates the position and orientation of thetelescope with respect to the night sky (the celestial sphere).

A further, truncated, alignment procedure is depicted in the alignmentflow chart of FIG. 10 b, in which an Alt-Az configured telescope isoriented to the night sky using only a single star alignment procedure.As with the previous case, a user is prompted to zero-in the motorposition encoders by pointing the telescope to the North and levelingthe telescope such that the altitude setting is at 0°. The user thenselects a particular star from an alphabetized stellar object databaselist and presses the enter key 113, causing the telescope toautomatically slew to the vicinity of that star. The user centers thestar in the,field of view of the eyepiece by depressing the positionkeys 112 as required. Once the chosen star is centered in the field ofview of the eyepiece the user again presses the enter key 113 thetelescope is aligned for a night of viewing.

Although the telescope might technically be considered “aligned” afterthe user follows the above-described one star alignment procedure, theaccuracy of the one star telescope alignment procedure should only beconsidered sufficient for general astronomical observations. Because ofcertain pointing errors that occur as the result of well knownastronomical perturbations, as will be described further below,additional observations and alignment steps should be incorporated intothe procedure to refine the accuracy of the initialization procedure.

Turning now to FIG. 10 c, a user definable two star alignment procedurewill now be described in connection with the illustrated procedural flowchart. As with the previous two alignment procedures, the telescopeundergoes an internal initialization prior to beginning the observationsession following which the LCD display 102 of the intelligent telescopesystem controller 100 displays a prompt screen requesting the user toselect an alignment procedure. If the user desires to align thetelescope with regard to two user defined celestial objects, the usermay scroll through the alignment to the two star alignment option andpress the enter key 113.

The system next prompts the user to point the telescope to the North, inorder to zero the azimuth axis position encoders, after which the userdepresses the enter key 113 to inform the system the telescope tube isin its appropriate azimuth position. Next, the system prompts user tolevel the telescope by adjusting the telescope's altitude position untilthe altitude (or declination) setting circle is set to 0°, thus zeroingthe altitude motor position encoders. As was described previously, allsubsequent motion of the telescope away from this pre-set 0,0 position,allows a telescope system to directly calculate its altitude and azimuthdisplacements from the 0,0 reference point. The user is then prompted toscroll through an alphabetized stellar object database listing andselect a particular star from the list by depressing the enter key 113.Again, once a particular user defined star is identified, the systemcontroller automatically slews the telescope to the vicinity of thatstar. When slewing is complete, the user is prompted to center that starin the field of view of the eyepiece using the position keys and, whenthe star is centered, the user depresses the enter key. The user is thenprompted to scroll through the alphabetized stellar object data baselisting and select a second particular star from the list. Again, theenter key is depressed indicating that the user has selected the secondstar. Once again, the system controller automatically slews thetelescope to the vicinity of the star after which the user is againprompted to center that star in the field of view of the eyepiece usingthe position keys. When the second star is centered the user depressesthe enter key and the system controller calculates the absolute positionof the telescope system with respect to the night sky.

Once the absolute position of the telescope system with respect to thenight sky is determined, the system microprocessor 121 is easily able tocalculate the path of any given celestial object through the sky and todevelop the appropriate motor motion commands in accordance with theabove-mentioned drive rate equations, such that an Alt-Az telescopesystem can smoothly and accurately track the object, i.e., “stops thesky” in software. A celestial object's motion through the sky will,necessarily, be calculated in terms of its rate of change in bothaltitude and azimuth as a function of time. Thus, for a given timeperiod, the system microprocessor 121 is able to calculate theincremental motor step or “tick” rates required to be executed by themotor assembly so as to allow the telescope to track the object as itmoves through the sky.

With regard to the foregoing alignment systems described in connectionwith the procedural flow charts of FIGS. 10 a, 10 b and 10 c, it shouldbe noted that the system controller calculates the telescope's positionby mapping the telescope's Alt-Az coordinate system (Cartesiancoordinate system) to the RA and Dec spherical coordinate systemdefining the night sky (the celestial sphere). In particular, the systemcontroller reads the telescope's altitude and azimuth angular positions,when pointed at the selected star or stars, by reading the altitude andazimuth motor position encoder values when the user depresses the enterkey after each star has been centered in the telescope eyepiece. Fromthe telescope pointing angles thus defined, the system controllercalculates the telescope's Cartesian position vectors and resolves eachposition vector into a matrix of direction cosines. The Cartesiancoordinate matrix is mapped into a similarly defined matrix of thedirection cosines of the star or stars expressed in terms of thecelestial coordinate system, using well understood mathematicaltechniques involving matrix manipulation and rotation. The matrix ofcelestial direction cosines is generated by evaluating the RA and Deccoordinates of the star or stars identified by the user during theselection procedures.

It will be evident to those familiar with the mathematical arts thatonce the same two points are identified in two different coordinatesystems, those two coordinate systems can be mathematically mapped toone another such that any further coordinates expressed in onecoordinate system are easily expressed in the other coordinate systemthrough a mathematical transform. Thus, once the telescope system isaligned with respect to the celestial sphere, further observations maybe made by merely expressing the location of a desired object in termsof its celestial coordinates. The system controller understands therelationship between the celestial coordinate system and the telescope'saltitude and azimuth coordinates, makes the proper mathematicaltransformation and drives the altitude and azimuth motors appropriatelyto point the telescope at the desired celestial position.

Once a telescope is “aligned” by use of one of the above-describedalignment procedures, the user might wish to further refine thealignment accuracy of the telescope system by refining the Cartesiancoordinate matrix defining the telescope's altitude and azimuth positionvector. As is well known in the art, certain corrections must be appliedto a celestial object's mean catalog of position in order to reduce itto the object's apparent position in the night sky. When an observerplans an evening's observations, the observer typically obtains anobject's RA and Dec coordinates from an ephemeris or catalog whichdefines the object's position in terms of the coordinate system of astandard epoch. This is the mean position of the object. However, thestandard epoch is generally different than the epoch at the time ofobservation. In addition, the object's catalog position does not includecorrections for certain positional errors which depend upon theobservation time and the particular location of the observer. Thus, thecatalog position does not define precisely where the observer wouldlikely find the desired object. Since the telescope's system controlleroperates on an object data base which defines celestial objectsaccording to their mean position taken from a catalog, the meancoordinates must be converted to apparent coordinates before commandsare sent to the telescope's altitude and azimuth motors, in order thatan object may be precisely acquired and tracked.

The corrections that must be applied to a catalog mean position in orderto reduce it to apparent position are listed in the following table, inorder of decreasing size.

TABLE 1 Approx. Correction Magnitude Precession  40′ of arc. Refraction 30′ of arc. Annual Aberration  20″ of arc. Nutation  17″ of arc. SolarParallax   9″ of arc. Stellar Parallax   1″ of arc. Orbital Motion   1″of arc. Proper Motion 0.5″ of arc. Diurnal Aberration 0.3″ of arc. PolarMotion 0.1″ of arc.Not all of the listed corrections need be applied, only thosecorrections larger than the required pointing accuracy of anobservation. Typically, only precession and refraction corrections needbe made.

Additional sources of systematic error come from certain mechanicalerrors introduced by imperfections in the telescope mount, the motor anddrive train system, the servo feedback system and imprecisions inleveling the telescope. Mechanical corrections that should be consideredwhen precisely aligning the telescope system are listed in the followingtable.

TABLE 2 Encoder Zero Offset Azimuth Axis Tilt (Alt-Az Mounts) Polar AxisMisalignment (Equatorial Mounts) Axis Non-orthogonality CollimationError Tube Flexure Mount Flexure Gearing/Bearing Error Drive TrainTorsion ErrorThese corrections are computed in a manner that can be used with anytelescope of a particular mounting type, but the values of the errorparameters are unique to each individual telescope system, since theyare characteristics of that system. For example, in closed loop systems,the position feedback encoders provide a numerical value correspondingto the angular position of an axis. This numerical value is converted toa meaningful coordinate, such as RA, Dec, altitude or azimuth, byapplying a calibration algorithm to the raw encoder data. These encoderzero offset corrections are incorporated into the calibration algorithmin order to provide numerical values representing the true position ofthe telescope. The system controller compares the apparent position ofthe desired object with the position of the telescope (determined fromthe position encoder readings) and generates appropriate movementcommands to the motors in order to minimize the difference between theobject and telescope positions.

Each of the astronomical and mechanical error sources are dealt with inprecisely the same manner as initial telescope orientation. Once thetelescope has been “aligned” the user may slew to a next object in orderto begin observation. If the next object is not precisely centered inthe telescope eyepiece, or if the next object drifts from the center ofthe eyepiece during tracking, the user may manually reposition thetelescope using the position keys and commands the system to re-sync tothe object's new position. The minor corrections, thus made, form thebasis for a refinement of the Alt-Az position matrix which is thenmapped into the celestial coordinate system. As further celestialobjects are evaluated, the matrix is further refined to account forfiner and finer error sources. Although capable of such further accuracydefinition, it will be understood that the system according to theinvention is able to account for, at least, the first two majormechanical error sources during the initial orientation procedure.Certain astronomical corrections are defined by well understoodmathematical algorithms and can be easily incorporated into theorientation procedure. Thus, the pointing and tracking ability of thetelescope system according to the invention is deemed sufficientlyaccurate for deep-sky observations and astrophotography following thealignment procedures set forth in connection with FIGS. 10 a, 10 b and10 c.

Since the system controller is operable to define telescope alignmentand movement with respect to a polar (equatorial) mount configuration,it is now appropriate to discuss alignment procedures associated with anequatorial mount in connection with the procedural flow charts of FIGS.11 a, 11 b and 11 c. Each of the polar alignment procedures firstrequires that the polar configuration and alignment mode is chosen by auser during system initialization as described in connection with theinitialization procedure flow chart of FIG. 12. Needless to say, it isalso necessary to that the telescope mount be configured as anequatorial mount and that the user properly adjusts the telescope'sdeclination axis such that the declination axis is perpendicular to themount's declination plane and that the celestial pole (North or Southdepending upon the observer's hemisphere) falls on the mount'sdeclination plane.

Turning now to FIG. 11 a, an “easy” polar alignment procedure isdescribed. Specifically, when the “easy” alignment procedure is selectedfrom the menu, the system prompts the user to point the telescope (usingmotion keys 112) along the RA axis until the telescope is pointed to thehorizon (RA home position). The user then depresses the enter key 113 toinform the system that the telescope tube is in its appropriate RAposition. Next, the system prompts the user to move the telescope untilthe declination setting circle reads 90°. Putting the telescope in ahome position with regard to both RA and Dec functions to zero-in theposition encoders of the declination and right ascension motors. Anysubsequent of the telescope away from its 0,0 position allows thetelescope system to directly calculate its right ascension anddeclination displacement from the 0,0 reference point.

After the previous steps are completed, the remainder of the “easy”polar alignment procedure is identical to the “easy” Alt-Az alignmentprocedure described in connection with FIG. 10 a. In particular, usingthe time and data entries provided by the user, the telescope systemconsults a data base of well known celestial objects and selects aparticular bright object which is currently above the horizon; thesystem automatically slews the telescope to the vicinity of that star bycommanding the appropriate motion from the right ascension anddeclination motors; prompts the user to center the star in the field ofview of the telescope eyepiece and uses the observer's manual positionadjustments to refine its orientation algorithm. The process is repeatedfor a next star which, when centered by the observer, allows the systemto calculate the precise position and orientation of the telescope withrespect to the night sky (the celestial sphere).

As was the case with the Alt-Az configuration, a truncated, one-star,alignment procedure is provided to support an equatorial mountconfiguration and is depicted in the procedural flow chart of FIG. 11 b.As with the previous case, a user is prompted to zero-in the motorposition encoders by commanding the telescope to move to its RA and Dechome positions. The user then selects a particular star from analphabetized stellar object data base list and may press the enter key113, causing the telescope to automatically slew to the vicinity of thatstar. The user then centers the star on the field of view of theeyepiece by depressing the position keys 112 as required. Once thechosen star is centered in the field of view of the eyepiece, the useragain presses the enter key 113 and the telescope is deemed aligned fora night of viewing.

A two-star alignment procedure is depicted in the procedural flow chartof FIG. 11 c, in which the user is again prompted to move the telescopeto the RA and Dec home positions and align the telescope by sequentiallyselecting two stars from an alphabetized stellar object data base list.As each star is selected, the telescope system automatically slews tothe vicinity of that star, following which the user centers the star inthe field of view of the eyepiece using the position keys 112 asrequired, and depresses the enter key 113 in order to inform the systemthat the desired star is centered.

Following definition of the home position, and following entry of eitherone or two stars in accordance with the above procedures, the telescopesystem calculates the telescope's position with relation to the nightsky. Since the telescope mount comprises an equatorial configuration,the computation algorithm is simplified somewhat since the system neednot convert coordinate systems, from, for example, Alt-Az to equatorial.Since an equatorial mount maneuvers in accordance with a sphericalcoordinate system defined by RA and Dec, all that is required to orientthe telescope is a simple rotation of the telescope spherical coordinatesystem into the celestial coordinate system. The rotation is made aboutthe telescope's RA and Dec axes in accordance with well establishedmathematical principles which need not be discussed further herein.

Following orientation, the equatorially configured telescope system isnow able to acquire and track selected celestial objects by appropriatemotion commands to its right ascension and declination motor assemblies.Once a selected celestial object is acquired, tracking is effectedsimply by commanding the right ascension motor assembly to move thetelescope about the corresponding right ascension axis at the siderealrate in the desired direction. No further commands need be given thedeclination motor assembly unless the user desires to acquire adifferent celestial object or, alternatively, the user desires to moreprecisely and accurately align the telescope system to compensate forsome slight originally unaccounted for error.

Returning now to FIG. 6 b, the system microprocessor 121 receives userI/O information, as provided by the system I/O microcontroller 122 andperforms any needed data processing under application software programcontrol. Data processing typically results in some form of desiredtelescope motion. The system microprocessor 122 is able to calculate thedirection and extent of any required motor motion and is further able todirect the appropriate motor assembly to take the required action bypassing the appropriate command through the system I/O microcontroller122. Motor motion commands are substantially the same as those describedin connection with the embodiment of FIGS. 5 a and 5 b and are providedto the system I/O microcontroller 122 over a two-wire serial clock anddata bus 132. Certain commands are passed through the microcontroller122 and are issued directly to the motor by the system microprocessor.Such commands typically include the step rate commands, the error countcommands, the set and find LED position commands, and the like. Certainother information, typically read data, is held and processed by thesystem I/O microcontroller 122 for use by the microprocessor when it sodesires.

Notwithstanding the foregoing discussion of telescope orientation andalignment, it will be evident to one having skill in the art, that majorsimplifications can be made to a telescope orientation and alignmentprocedure by incorporating additional component devices that are able toautomatically provide an indication of the orientation of the telescopetube with respect to the compass, i.e., north-south sensing, anautomatic indication of axial tilt, i.e., telescope level, and anautomatic indication of absolute position and time. Pertinent toalignment and orientation simplification is the realization thatelectronic compasses, based on magnitoresistive sensors are able toelectrically resolve a position orientation using the earth's magneticfield, to an accuracy of approximately ½ degree and with a resolution ofabout 0.1 degrees. As is well understood by those having skill in theart, the earth is surrounded by a magnetic field which has an intensityof from about 0.5 to about 0.6 gauss and includes a component parallelto the earth's surface that always points towards magnetic north. Thisfeature of the earth's magnetic field forms the basis for all magneticcompasses and it is the components of this field, parallel to theearth's surface, better used to determine compass direction.

In particular, a type of magnetic sensor, termed a magnitoresistivesensor (MR) is constructed of thin strips of a nickel iron (NiFe)magnetic film, also termed permalloy, whose electrical resistanceproperties vary with a change in an applied magnetic field. MR sensorshave a well defined axis of sensitivity, respond to changes in anapplied magnetic field as little as 0.1 milligauss, have a response timeof less than 1 microsecond and are generally commercially available aspackaged integrated circuits. MR sensors are thus particularly suitablefor use in a north-south sensing apparatus coupled to the telescopesystem of the exemplary embodiments.

One such configuration is shown in FIG. 17 which is a semi-schematiccircuit diagram of a north-south sensor system, in accordance with theinvention, that incorporates an MR sensor, implemented as an HMC 1021S,manufactured and sold by Honeywell, Inc. of Plymouth, Minn. The MRsensor 200 is a magnitoresistive sensing element constructed of NiFethin films deposited onto a silicon substrate in a manner to define aWheatstone resistor bridge. The MR sensor 200 further incorporates acurrent strap which is used to electrically “set” or “reset” thepolarity of the device output and further allows a compensating offsetfield to be applied to the sensing elements to compensate for ambientmagnetic films. A supply voltage is coupled to the MR sensor and causesa current to flow through the magnitoresistors comprising the Wheatsonebridge configuration. A crossed applied field causes magnetization intwo of the oppositely placed resistors to rotate towards the current,resulting in an increase in the corresponding resistance. In theremaining two oppositely-placed resistors, magnitization rotates awayfrom the current resulting in a decrease in the resistance.

Current passing through two of the arms of the Wheatstone bridge istaken from the MR sensor at two outputs, one of which is applied to thenon-inverting input of an operational amplifier 202 configured as avoltage follower. The second output is applied to the non-invertinginput of a second operational amplifier 204, the inverting input ofwhich is coupled to receive the output of the voltage follower 202. Theoutput of the second operational amplifier 204 is directed to thenon-inverting input of a gain stage 206 which, in turn, drives an outputpin 208 to give an indication signal as to whether or not the MR sensoris aligned with the earth's magnetic field. In operation, the gain stage206 is configured so as to output a signal if the current from the MRsensor's two outputs is unbalanced, i.e., indicating that the sensor isnot aligned with the earth's magnetic field. As the center comes intoalignment with the field, current through the oppositely-placed resistorarms becomes balanced, resulting in the second operational amplifier 204having a null output. Gain stage 206, in turn, outputs a null signalindicating that the MR sensor is aligned with the earth's magneticfield, i.e., pointing towards magnetic north.

As a further indication of whether or not the MR sensor is pointingtowards magnetic north, two light emitting diodes 210 and 212 arecoupled, in parallel fashion, to the output of the gain stage 206. Afirst light emitting diode (LED) 210 is reverse coupled to the output ofthe gain stage 206. By reverse coupled, it is meant that the negativeside of the diode is coupled to the output, while the positive side iscoupled to a reference potential, such as ground. A second diode 212 iscoupled in forward fashion to the output of the gain stage 206. Incombination, the diodes function to give an indication as to thealignment of the MR sensor with earth's magnetic field. When the sensor200 is mis-aligned in one direction, the gain stage output will beeither positive or negative, depending on whether the sensor ismis-aligned to the “left” or “right” of a centerline indicating thedirection of magnetic north. When the sensor is mis-aligned to onedirection, the gain stage output might be negative, in which case thefirst LED 210 (the negatively coupled LED) will conduct current, therebyemitting light. If the MR sensor 200 is misaligned in the oppositedirection, the gain stage 206 will output a positive signal, causing thepositively coupled LED 212 to conduct, lighting-up in turn. When thesensor is aligned to magnetic north, the gain stage output is nulled andboth LEDs are off.

It should be noted, that since these are diodes, there is a forwardvoltage drop associated therewith which limits their precision inindicating magnetic north precisely. Depending on the value of theforward voltage drop of the LEDs 210 and 212, the MR sensor has a slightrange about true north during which time the gain stage 206 will notdevelop a sufficient output signal to activate either the forward orreverse biased LED. However, even within this “uncertain” range, thegain stage 206 is outputting a signal to the output pin 208 which isable to be evaluated by either an intelligent system control unit (100of FIGS. 6 a and 6 b) or an integrally coupled PIC processor of the typedescribed above.

It bears mentioning further that the MR sensor system is able to becalibrated by a zero adjustment circuit 214 which is coupled to theinverting input of the second operational amplifier 204. Zero adjustmentcircuit 214 is provided in order to compensate for the input offsetscommonly exhibited by almost all operational amplifiers, and suitablycomprises an adjustable resistor coupled between positive and negativesupply voltages with a center tap defining the zero adjustmentconnection to the inverting input of the operational amplifier 204. Inoperation, the sensor is precisely aligned with the earth's magneticfield in a manufacturing jig and the variable resistor is adjusted untilsuch time as the gain stage 206 defines a null output signal. Thisindicates that the overall circuit is now balanced with circuit offsetscompensated for.

Further, the sensor circuit suitably includes a set/reset circuit,suitably configured as a current pulse generator, which is used toeliminate the effects of past fail hysteresis and which canelectronically set or reset the polarity of the output by applying anappropriate set or reset signal.

The MR sensor arrangement depicted in FIG. 17 has particular utilitywhen configured on a small printed circuit board and mounted on atelescope tube in such a manner that the position axis of the center isaligned with the long axis of the telescope. Therefore, when the MRsensor is aligned with the earth's magnetic field so as to indicatemagnetic north, the telescope tube is also positioned with its opticalaxis aligned towards magnetic north. The sensor's output 208 is coupledto the auxiliary input of the electrical interface (30 of FIGS. 3 a and3 b) and is thereby made available to system processing components as anautomatic direction indication signal. In this manner, there is nolonger any need for a user to manually align the telescope to pointtowards north. Once the automated telescope system is turned on, anapplication routine automatically slews the telescope back-and-forth inthe horizontal direction and examines the “sense” of the output of thesensor. Once the automated system detects that the sensor is alignedcorrectly with north, i.e., senses a null output, the automatedtelescope system evaluates the position of the motors and initializesthe azimuth motor assembly.

While the discussion above has concerned itself with a description ofhow an MR sensor system is configured to align its self with the earth'smagnetic field, i.e., give an indication of magnetic north, it should benoted that the sensor can be configured to give an indication of itsalignment with respect to true north. In this particular instance, thesensor system is aligned with true north in a manufacturing jig and thezero adjustment circuit 214 is adjusted such that the gain stage 206outputs a null indication. It should be understood that the currents inthe oppositely-disposed arms of the Wheatsone bridge will necessarily beunbalanced, but the zero adjustment circuit 214 is adapted to compensatefor this misadjustment as well as compensate for any offsets developedby the operational amplifiers 202 and 204.

It is also quite within the contemplation of the present invention touse an MR sensor in a 3-axis mode in order to eliminate axial tiltconcerns by electronically dealing with any axis non-orthogonality. Inthis implementation, an additional MR sensor is provided which isaligned in a plane orthogonal to the plane of the horizontally disposedMR sensor. The additional MR sensor is configured to measure thevertical portion of the US magnetic field, i.e., the angle of themagnetic field to the surface of the earth. Errors introduced by axialtilt can be quite large depending on the magnitude of the dip, orinclination, angle.

An additional method that might be used to correct for axial tilt is toincorporate an inclinometer, or tilt sensor, with the MR sensor in orderto electrically define any mount offsets due to mount pitch. When aninclinometer, or tilt sensor, is incorporated with the MR sensor, thetelescope system is provided with a fully automated, electronicmethodology for 3-axis sensing. This allows the telescope system toautomatically adjust itself to a level condition as well asautomatically adjusting itself to align with either true or magneticnorth. Once these alignments are made, the axis encoders of the motorsystems are automatically initialized in order to compensate for themount alignment parameters. Therefore, electronic sensors coupled to thetelescope tube provide a very repeatable position index when inproximity with the mount's axis crossings. Electronic sensors are usedas fixed point high-resolution devices, with fine positioning beingprovided by the motor encoders. Since pointing accuracy typicallydepends on the flexure characteristics of a tube, the mechanicalstability of the tube and mount combination and the quality of thegearing between the drive motor and a telescope mount, it will beunderstood that pointing accuracy can be simply and easily added to ainexpensive telescope system that might exhibit a certain mechanicallooseness.

As was developed above, in order to completely align a telescope system,the user or an intelligent telescope system need only know the directionof north, the inclination of the horizon (level), the time and date andits position on the earth's surface. If these quantities are known,there is no further information that need be provided to any telescopesystem to allow it to thereafter point to any designated object with aknown ephemeris, other than an command to do so. Time and dateinformation are accessible by receiving a broadcast signal, WWV, whichis made available for such purpose. The automated telescope systemaccording to the invention fully contemplates being able to couple asource of WWV information into the intelligent system control unit sothat the control unit is able to continually update date and timeinformation such that the time and date variables of the alignmentsystem are eliminated. WWV is in Fort Collins, Colo. and broadcastscontinuous time and frequency signals on 2.5, 5, 10, 15 and 20 MHz. Allfrequencies provide the same information, with frequencies above 10 MHzworking best during daylight hours, while lower frequencies working bestat night. The beginning of each hour is identified by a 0.8 second long1500 Hz tone, with the beginning of each minute identified by a similarlength 1000 Hz tone. Second pulses are given by a 440 Hz tone the 29thand 59th second pulses of each minute being omitted. Time signals may beinput directly from a WWV receiver, with the various frequency tonesdefining clock signals which can be processed by the intelligent systemcontrol unit to update its date and time information.

Alternatively, WWV information may be received via an Internetconnection by a laptop-type personal computer system. Informationprocessed by the laptop can be transferred to the intelligent systemcontrol unit over the auxiliary input bus of the interface panel in amanner as described above.

Accurate location information can be provided to the intelligent systemcontrol unit by use of a global positioning system (GPS) or differentialglobal positioning system (DGPS) receiver configured with an NMEAinterface. The NMEA interface is a well recognized interface protocolwhich can additionally be coupled to the auxiliary interface to proved asource of location information directly to the intelligent systemcontrol unit. Once the intelligent system control unit has location,time and date information available as well as the output of the “north”and “level” sensors, the intelligent system control unit becomes fullyaware not only of its location but also of the spatial orientation ofthe telescope system to which it is coupled.

The systems and methods associated with 3-axis sensing, as describedabove, are equally applicable to additional “pointing” or “acquisition”devices beyond the novel telescope system in accordance with theinvention. Indeed, 3-axis sensing systems are adaptable to be mounted ona detachable viewfinder or telescope eyepiece such that a user need onlydirect the eyepiece in accordance with the signals received from thesensing devices in order to orient themselves with both horizon and withnorth. Binoculars and heads-up-display (HUD) goggles are also able to beconfigured with 3-axis sensing devices in the above manner in order toprovide them with an orientation capability.

A further feature of the intelligent system control unit (100 of FIGS. 6a and 6 b) is the construction of the light source for providing uniformillumination to the LCD display screen 102. With reference, now, to FIG.13, a cusped, curvilinear optical light box 150 is disposed on thesurface of the control unit's electronic component circuit board, andpositioned in the region just beneath the LCD display screen, and havingapproximately the same footprint. The light box defines a generallyrectangular, hollow enclosure, with its surface describing a pair ofcurvilinear arcs 151 and 152, laterally symmetrical about a central,downward projecting, cusp which bisects the surface. Illumination LEDs153, 154, 155 and 156 are arranged, in pairs, along each of the shortsides of the light box and are configured to shine into the enclosure,in the direction of the cusp.

Each of the curvilinear surfaces are rendered translucent, by paintingthem white, for example, or by constructing the reflector from atranslucent material such as a suitable plastic. The translucentproperty of the surface allows the light developed by the LEDs to shinethrough the surface, but permits each arcuate portion to diffuse thelight and direct it (as a backlight source) onto the LCD display in adiffusion pattern promoting uniform illumination.

In a conventional, flat-surfaced light box, light energy, from anon-coherent, uniform, source such as an LED, is scattered through thetranslucent surface only when the scattering vector of the light makes arelatively large angle with the surface in question. As the surfaceelement is farther and farther away from the light source, thescattering angle becomes correspondingly smaller, until the light isscattered along the surface underside (perpendicular scatter vector) andvery little is scattered through the material and onto the display(Normal scatter vector). This phenomenon results in a dark, orrelatively unilluminated, region in the center of the display, while theedges are over illuminated (so called hot spots). This makes the displayhard to read, particularly at night.

The curvilinear arcuate surfaces of the light box 150 according to theinvention, are shaped to insure a substantially greater degree of normalscattering out of the light box at the light path extremities, i.e., theportion of the surface farthest from the light source (the center).Moreover, the gradual curvature of each surface maintains the surface ata relatively constant scattering angle with respect to the light source.Thus the light energy diffused through the surface is relativelyconstant along the surface in the direction from the light sourcetowards the cusp. In the region of the cusp itself, surface reflectionadds an additional component of illumination to the light directed ontothe display. Light scattered from a first arcuate surface 151 at a lowangle, is reflected from the second arcuate surface 152 at an equalangle and thus towards the display. Low angle surface scattering istherefore recovered to some degree and forms an additional component ofillumination in the central region.

It should be evident, from the foregoing discussion, that the variouscomponents and elements of the present invention are not limited to theparticular telescope systems illustrated thus far. Indeed, the telescopeand motor systems described in connection with the illustratedembodiments, were chosen because the novel components of the inventionappeared externally and admitted of more direct identification. Turningnow to FIG. 14, there is depicted a further embodiment of a fullyautomated telescope system, in which the motor assemblies are notconfigured as add-on components, but rather are integrated into thetelescope system.

The telescope system of FIG. 14 is shown as configured to operate inequatorial mode, with its legs 160 a, 160 b and 160 c positioned toequatorially align the telescope such that the top surface 161 of thebase housing 162 rotates to define the system's RA plane. Right and leftfork arms 163 and 164, respectively, support the telescope tube 165 andprovide its declination rotation axis. The base housing 162 additionallysupports an interface panel substantially similar to the interface panel30 of FIGS. 1, 2, 3 a and 3 b, but without the serial interfaceconnections to the Alt (Dec) and Az (RA) motor assemblies. Rather, theinterface panel 166 provides for plug-in connection of either of thepreviously described control units, and for plug-in connection of amultiplicity of auxiliary devices through an auxiliary bus.

Motor assembly coupling connections are not required for the embodimentillustrated in FIG. 14, since the motor assemblies are incorporated intothe telescope structure. Thus, external connections are not required.However, electrical connection to the motor assemblies is made via anidentical 2-wire serial interface as with previous embodiments, exceptthat the motor interface busses are internalized into the telescopestructure as well.

A first, declination (or altitude) motor assembly is configured into amotor enclosure 168, formed by in the hollow interior of one of the forkarms; the right fork arm 163 in the illustrated embodiment. FIG. 15depicts the internal configuration of the fork arm 163 and illustratesthe position of a declination (Alt) motor assembly 170 and itsassociated gear train 172 within the fork arm.

A second, right ascension (or azimuth) motor assembly is configured tofit within the base housing 162 of the telescope system, in a mannerdepicted in FIG. 16. The RA (Az) motor assembly 174 and its associatedgear train 176 are disposed in a hollow enclosure formed just beneaththe RA surface 161 of the telescope. Direct DATA, CLK, power and groundcouplings are taken from hardwired connections made between the controlunit input of the interface panel 166 and each respective motorassembly. Each motor assembly 170 and 174 comprises the same electroniccomponents as those described in connection with previous embodimentsand are, therefore, endowed with the same degree of intelligence.

The telescope system embodiment of FIGS. 14, 15 and 16 may be controlledby either the semi-intelligent or fully intelligent control unitsdescribed previously, with the same degree of functional performance.Moreover, the auxiliary bus supports the same numbers and types ofauxiliary devices.

It should be understood, therefore, that distributing intelligenceacross various functional components of a telescope system, is notlimited to the particular configuration of the telescope. Certainportions of the system may be integrated into the telescope in theinterest of compactness and design efficiency without sacrificing any ofthe virtues of intelligence distribution. All that these integratedsystems lack is the ability to be lobotomized to a purely mechanicalsystem operated entirely by manual manipulation.

1. In a computerized telescope system of the type including a telescopecoupled for rotation about two orthogonal axes, together with first andsecond axial position indicators, one coupled to each axis, a method fororienting the telescope system with respect to a spherical coordinatesystem, the method comprising: activating a central control processor,the central processor connected to receive positional information fromeach position indicator; using the central control processor to receivea rotation metric, the rotation metric rotating a virtual telescopeposition in the spherical coordinate system in accord with a major axisof the spherical coordinate system; using the central control processorto receive a geographic input; moving the telescope about a first one ofthe axes to a first terrestrial reference position; communicating,between the central control processor and the first axial positionindicator, a first reference value corresponding to the firstterrestrial reference position; moving the telescope about the secondone of the axes to a second terrestrial reference position;communicating, between the central control processor and the secondaxial position indicator, a second reference value corresponding to thesecond terrestrial reference position; and processing the first andsecond reference values and the rotation metric so as to define avirtual coordinate location of the telescope system with respect to thespherical coordinate system.
 2. The method according to claim 1, furthercomprising: accessing a database of celestial objects; automaticallyselecting a celestial object, known to be above an observer's horizon,from the database; and automatically moving the telescope to pointtowards the selected celestial object.
 3. The method according to claim2, reading a first set of positional data from the respective axialposition indicators when the telescope is pointing towards the selectedcelestial object; evaluating the position of the selected celestialobject in a viewing field of the telescope; positioning the selectedcelestial object in a central region of the viewing field; reading asecond set of positional data from the respective axial positionindicators when the selected celestial object is positioned in thecentral region of the viewing field; and processing the first and secondsets of positional reference data to refine the virtual coordinatelocation of the telescope system with respect to the sphericalcoordinate system.
 4. The method according to claim 3, wherein thespherical coordinate system is the celestial coordinate system andwherein the orthogonal telescope axes define an alt-azimuth mountconfiguration.
 5. The method according to claim 4, wherein the positionreference indicators comprise encoders coupled to their respective axes,each encoder defining a displacement of the telescope about itsrespective axis, the displacement based on the respective first andsecond reference values.
 6. The method according to claim 5, wherein thefirst terrestrial reference position is a determinable angle withrespect to North and wherein the second terrestrial reference positionis a determinable angle with respect to horizontal.
 7. The methodaccording to claim 6, wherein the geographic input is a latitude andlongitude of the telescope location.
 8. The method according to claim 7,wherein the rotation metric is a time of day.
 9. The method according toclaim 8, further comprising: coupling a global positioning systemreceiver to the central control processor; and receiving the geographicinput and the rotation metric from the global positioning systemreceiver.